The purpose of meditation is to quiet the chattering mind. The practice of meditation takes us away from the familiar everyday thinking mind to the less familiar quiet mind. It helps us to get re-acquainted with our inner quiet mind, to befriend it, to be comfortable with it and to embrace it. Ultimately, what we want to do is to reclaim it as our own and to abide in it.
After all, this is the abode of the Gods (brahma vihara).
How do you quiet a chattering mind? The answer is by tying it to a post. In this way, the chattering mind, like a monkey, can run and jump from one place to another, but always within the confine and perimeter of the rope and post until it eventually tires itself up and rest. This is actually what happens when you focus your mind on a single object of meditation. This is thought directed (vitaka) and sustained (vicara).
Once the chattering mind loses steam, it takes less effort to sustain the concentration on the object of meditation. As the concentration increases from access concentration to absorption concentration, the focus, clarity and energy of the mind increase in tandem. You are now beginning to get face to face with the nature of the quiet mind. As your sense of pleasure (piti) and happiness (sukha) increase, your focus becomes more and more one-pointed (ekagatta).
When finally all pleasurable and happy sensations fall away, leaving only one-pointedness of the mind, you have now entered into the fourth jhana. It is at this level that psychic phenomena can be experienced.
However, one need not wait until the achievement of the fourth jhana to benefit from the fruits of meditation, the rewards of a quiet mind. This is because as your mindfulness and concentration increase, your resistance and struggle decrease, and that in itself takes you closer to the core of your manifestation, your essence.