The railway engine moves. All these are instances of concentrated waves. Even so, if you collect the dissipated rays of the mind and focus them at a point, you will have wonderful concentration. Real Raja Yoga starts from concentration. Concentration merges in meditation.
Concentration is a portion of meditation.
Meditation follows concentration. Jivanmukti leads to emancipation from the wheel of birth and death. Therefore, concentration is the first and foremost thing a Sadhaka or aspirant should acquire in the spiritual path. You are born to concentrate the mind on God after collecting the mental rays that are dissipated on various objects. That is your important duty.