Here, we should know the difference between Samatha meditation and Vipassana meditation. Samantha means concentration , calmness, tranquility. When the mind is deeply concentrated on the object of meditation, the mind become calm and tranquil. The purpose of Samatha meditation is to attain deep concentration of the mind on a single object. So, the result of Samatha meditation is the attainment of deep concentration such as absorption (appana samadhi, jhana) or access concentration (upacara samadhi). When the mind is deeply concentrated on the object of meditation, all the defilements such as lust, greed, hatred, desire, conceit, ignorance and so on are kept away from the mind which is absorbed in the object. When the mind is free from all the defilements or hindrances, we feel calm, tranquil, happy and peaceful. The results of the Samatha meditation, therefore, is some degree of happiness through the attainment of deep concentration such as Absorption (appana samadhi, Jhana) or access concentration (upacara samadhi) but it does not enable us to rightly understand the mental and physical phenomena as they really are.
A Samatha meditator has to make some device or kasina as the object of meditation. For instance, to make a colour kasina, he has to make a red circle on the wall about two feet from the floor in accordance with the Visuddhimagga commentary. He must make the red circle about the size of a plate and the colour must be of pure red, even and smooth. When the device has been made, then he has to sit on the floor about two feet from the wall, look at the red circle and concentrate on it. Should the mind wander, he must not follow the mind but he must bring it to the object of meditation, i.e., the red circle. He must focus the mind on the red circle and and observe it as red, red, red. This is the way of Samatha meditation in brief.
As for Vipassana meditation, the purpose is to attain the cessation of suffering through rightly understanding mental and physical processes in their true nature. For this, we need some degree of concentration. This concentration can be attained through constant and uninterrupted mindfulness of the mind body process. Thus, we have a variety of objects of meditation: happiness is an object of meditation and so is anger, sorrow, painful sensation, stiffness, numbness and so on. Any mental or physical process can be the object of meditation.
The purpose and the results of Samatha and Vipassana meditation are different, as are the methods.
We should go back to what I explained earlier. When we walk, we observe the movement of the foot - the lifting, pushing and dropping. At the beginning of the practice, our mind is not well concentrated on the foot. When the mind wanders, we have to follow it and observe it as it is until that wandering mind has disappear. Only after it has disappear, do we note the movement of the foot as usual. When the mind becomes well concentrated on the movement of the foot, what we note is the movement of lifting, pushing and dropping and we must not be aware of the form of the foot or the form of the body during walking. When the foot is lifted, the mind notes it as lifting, when the foot is pushed forward, the mind notes it as pushing, when the foot is dropped, the mind notes it as dropping. When we come to realise them as natural processes of movement, we also come to realise the mind that notes them. The lifting movement is one process and and the mind that notes it is another process. The pushing movement is one process and the mind that notes it is another process. In this way, we thoroughly realise the two processes of mental phenomena and physical phenomena. We rightly understand this dual process as just natural processes of mental and physical phenomena. We do not take them to be a person, a being and I or you. Then there will not arise any false concept of personality, individuality, soul or self. When this false concept has been destroyed, there will not arise any attachment or desire which is the cause of suffering (dukkha). So, because attachment does not arise, there will not arise any dukkha which is actually the results of the attachment. We attain the sensation of suffering at he moment of experiencing the process of the movement the lifting, pushing and dropping movement - as just a natural process.
As we proceed, our mindfulness becomes more constant, uninterrupted and powerful. As the mindfulness becomes constant and powerful, the concentration become deeper and stronger. When the concentration becomes deep and strong, then our realization or penetrating insight into mental processes and physical processes become clear. So we come to realise many series of lifting movements arising and passing away one after another. During such experience, we come to understand that no part of the process is permanent or everlasting. Every process of movement is subject to impermanence (anicca) - arising and passing away very swiftly, so it is not a good precess; it is bad. Then we come to realise one of the three characteristics of the mental and physical process, i.e. dukkha. When we realise the impermanent and suffering nature of this physical process of movement, then we do not take it to be an everlasting entity - a person, a being, a soul or a self. This is the realization of theanatta, no soul, no self, non ego nature of bodily and mental processes. So we realise the three characteristics of mental and physical phenomena, Impermanence (anicca), suffering (dukkha) and no soul or no self (anatta).