Meditation is a means to train the mind. By repeating certain mental exercises —like fixing the attention on one point for awhile, or experiencing the whole body— the mind becomes more able to do those things. Just like when we train a muscle: Repeat the action and you get better at it.
From another perspective, meditation is a means to clear the mind of unconscious patterns and complexes. By entering the meditative state, we allow repressed memories and traumas to surface and dissipate, while we remain as the passive observers of this process.
Meditation is the key to your subtle energy body. When you meditate, you do for the subtle body the same thing you do to your physical body when practicing bodybuilding… you increase the beneficial energies, you expand the limits of your consciousness. But unlike the physical body which is limited in size, the energy body is not limited at all – you can make it expand until it is infinite.