Meditation is the art of maintaining the mind focused on a single thought. Why single thought; because mind is flow of thoughts only and by giving it a single thought one is actually destroying the realm of mind. When mind is constant chanting a mantra it is tried to give it a single thought and at the same time avoiding the all other thoughts. It is said to be a single-pointed meditation; same is applicable in case of ‘trataka’ and focusing of awareness at the point between two eye-brows. By doing meditation we are not only sublimating our mind but also integrating subjective mind and objective minds.
On the path of evolution, meditation is the final gateway through which every seeker must pass to gain the ultimate experience of the absolute Reality.
Actually there are two terms - 'Self' and a 'not-self'. 'Not-self' exists due to ignorance and it exists unless one break the realm of mind. Because beyond mind there is 'Self' and due to ignorance or 'maya' one thinks on the thoughts of 'not-self'.
With meditation one is continuously diluting the layers of mind and finally the mind get deleted and at that right moment one simultaneously realizes the 'Self'.