Deprotonation

Deprotonation is the removal of a proton (H+) from a molecule, forming the conjugate base.

The relative ability of a molecule to give up a proton is measured by its pKa value.
A low pKa value indicates that the compound is acidic and will easily give up its proton to a base.
The pKa of a compound is determined by many things, but the most significant is the stability of the conjugate base, which is determined mainly by the ability (or inability) of the conjugated base to stabilize the negative charge.