One is the concentration of the mind, and the other is called Pranayama (suppression of vital airs). Pranayama is said to be real; while concentration of mind is unsubstantial to it.
एकाग्रता च मनसः प्राणायामस्तथैव च। प्राणायामस्तु सगुणो निर्गुणो मनसस्तथा॥