Starting with "contact" of, let's say an apple; I see an apple (six sense base); I have a pleasant feeling (vedana) towards that apple; I want, crave, have interest in (tanha) that apple. Where i get confused is the "clinging" (upadana) part. can it be said that clinging is the continual "craving" for the object in question? is "attachment" tanha or upadana?
This is my confusion. I see both tanha and upadana as the same. But the Buddha makes a distinction between the two, so i would like to understand this distinction.
The Patha V's Apple
Tanha is a word that stands for hunger and thirst. Say: audisa?T.h.A (with a little tiny "h" sound) nHA (de-emphasized. Note the similarity to the "Hung" of hunger and the "Thur" of thurst.
Upadana you already knew about when you studied Giving, dana, in this case as in "Given", as in "Given over to" upa = uP Past.
I think you don't want to start at "phassa" "contact". I think to . . . um . . . grasp the evolution, you want the full context, so:
We start from the point of being blind to the final outcome: ageing and death, grief and lamentation, pain and misery, and despair.
Because we do not see the final outcome, we engage in actions of mind, word-thought-and speech, and body that inject the idea of "own-ness" into their karmic outcomes (sankhara -- what I call sankharaming).
Because we previously sankharamed, thus creating a world of "our own" in which to experience things, we have a consciousness of an "our world".
At this level it is seen as made up of two aspects: the mental and the physical.
Some descriptions of the paticca-samupada re-introduce consciousness here -- on one level, I believe, to distinguish between what one might call perception and consciousness, and on another level to distinguish between consciousness that has not yet become identified with individuality and that knowing which has become re- (vi) known as "my" consciousness.
This "our world" is made up by the grouping together of the six senses on the "inside" (the part of our world we identify as ourself) and the six types of objects of sense (the part of our world we identify as "other"): the salayatana or realm of the senses.
These two groups of phenomena (the sense spheres and consciousness: it requires three things for sensory consciousness to arise: the sense organ, the sense object, and consciousness) are constantly banging up against one another and this is (phassa, contact, touch).
Arising from this touch is sense experience. This is not "feeling" as you have it...how you feel about something (like, dislike, etc), this is raw sensation: it feels pleasant, unpleasant, or has no particularly pleasant or unpleasant sensation connected with it.
Here most descriptions of the patica-samupada do not go into the details of what is happening between this sense experience and the appearance of desire or tanha, but elsewhere, in the descriptions of how the khandhas work, we have the understanding (speaking here in terms of the operation going on "in" the individualilzed world; the non-individualized consciousness standing to one side, so to speak, observing; it, itself, having been produced by an exactly similar process in the earlier, sankaraming stage where the objects of contact was not the sense organ and sense object, but "raw" nama and rupa) that from the contact of the sense object with the sense organ arises sense experience, from the arising of sense experience perception, from the arising of perception consciousness.
Inserted on top of that process is the experience of the consequence of sankaraming: it is at this point that old kamma gets it's chance to bear fruit and with that fruit comes the experience of the intent connected with old actions along with an idea of "me-ness" or "my-ness".
If it were not yours, in your world, nothing connected with it could effect you, because it has become yours in your world, you experience that pleasant or unpleasant experience connected with it. Based on that pleasant or unpleasant sense experience is liking and disliking...both aspects of tanha (or something closer to your "feeling")
Here the individual has a choice. Endure the ending of the sense experience and the passing off of the wanting or wanting to get away and bring an end to the cycle, or begin a course of action erroneously designed to get away from the unpleasant or get the pleasant. This is where one has begun to get involved, upadana the up rising of giving in. And this you might say more or less encompasses the whole of the previous in that this grasping or what I call going-after-getting, is based in blindness and ends up creating and so is a sort of synonym for sankara.
Here the individual should reflect: "That which is being experienced is a thing of the past. It happened as a consequence of contact which occurred before this "I" was consciousness of it. Should I attempt to try to get this, or to get away from this, what I would be doing is going after something that is already done and gone. It would therefore be impossible for me to either get this or get away from this and what I would be doing is only simply creating something new. If he makes such a reflection and acts in accordance with that (not-doing, enduring the ending) to this degree, he has brought an end to pain.
If he make no such reflection he goes on to Living, Birth, Ageing and Death, Grief and Lamentation, Pain and Misery, and Despair.
Bhante Punnaji's view is that this term stands for the personalization process, Bhante Thanissaro holds that this term stands for fuel or sustenance (for continued rebirth).
Taking the statement: "Monks, there are these four kinds of grasping (upadana)...the grasping of sense pleasures, the grasping of view, the grasping of rule and custom, the grasping of the theory of self"  as basis, I would reconcile the various views this way:
Bhante Punnaji sees sense pleasures, view, rule, custom, and theory of self as the place where acting to get imparts personalization. I have this occuring at Sankhara, but there is really no big problem seeing upadana as sankharaming (the act and consequence of the act of body, speech, or mind that results in personal experience).
Bhante Thanissaro sees sense pleasures, etc, as the objects of the desire (that which sustains or fuels the desire) that wishes to recreate the sensation experienced from previous contact.
Taking the raw surface term of either of these two Bhikkhus, there is a part of the process between the experience of tanha and it's result in living that is missing. The how part.
On the one hand: How does downbound tanha rebound in personalization (Bhk. Punnaji), or in sense pleasures (Bhk. Thanissaro)? and on the other hand, how does downbound personalization, sense pleasure, rebound in living (bhava)?
I say this is easily enough seen by just observing the process in ordinary experience: Previously we ate a MacDonald's hamberger and experienced a pleasant sensation as a consequence. Now we are hungry again and we wish to re-create that experience. What do we do? We act on our desire...and more important, as in reverse it confirms the point of the paticca samuppada as the way out: if we don't act, we don't get. We go after, grasp after the fulfilment of tanha; this going after results in our "living" in a new situation. So the translators that use "grasping" are coming closest to the needed meaning here.
Majjhima Nikaya I, Middle Length Sayings or Discourses.
38. Mahatanhasankhaya Sutta (Mahaata.nhaasankhaya), I.256
WP: The Greater Discourse on the Destruction of Craving, 349
PTS: Greater Discourse on the Destruction of Craving, I.311
Mahatanhasankhaya Sutta The Major Discourse on Destruction of Craving (Part 2/2) Mahayamaka Vagga, Mulapannasa, Majjhima Nikaya, Suttanta Pitaka From 'Twenty-five Suttas from Mulapannasa' Burma Pitaka Association (Myanmar Tipitaka Association), 1989
Footnotes and references:
See Lesson 3 and The Great Master's Satisfaction Pastures: The Satisfaction of Sense Experience
In Awakening Meditation and various essays Bhante Punnaji holds that this term stands for "personalization." For Bhante Punnaji and some essays see: http://www.buddhadust.org/dhammatalk/dhamma_talk/ven_punnaji.htm; for a review of Awakening Meditation see: http://www.buddhadust.org/dhammatalk/book_reviews/awakening_meditation.htm.
For Bhikkhu Thanissaro's understanding, see: Mind Like a Fire Unbound: 2.2, where he holds that this term stands for fuel or sustenance. Taken figuratively as the fuel or sustenance of rebirth, this does not cause a problem with the idea of grasping; taken as the object of thirst, the fuel that or sustenance that keeps thirst going, it causes the same gap between the experience of thirst and the attaining of birth that bothers the Punnaji interpretation.
Majjhima Nikaya, Culasihanada Sutta, I.63
WP: The Shorter Discourse on the Lion's Roar, 159
PTS: Lesser Discourse on the Lion's Roar, I.85
ATI: The Shorter Discourse on the Lion's Roar
The previous quote is followed by a discussion of two views of becoming (bhava, the view of the eternalists, and vibhava, the view of the annihilationists), the point of which was to say that not understanding the rise and fall, attraction and peril of these views was to be not enlightened. Upadana then follows as that which gives rise to the views of bhava. Note: not bhava itself.