Point of the Contra-flexure is the point where Bending moment value is 0. or other way where Bending moments begins to change.
Flexural reinforcement may be reduced at this point. However, to omit reinforcement at the point of contraflexure entirely is inadvisable as the actual location is difficult to be identified in reality. Additionally, an adequate quantity of reinforcement should extended beyond the point of contra flexure to develop bond strength and to facilitate shear force transfer.
The significance of this point is that "Flexural reinforcement may be reduced at this point". In a bending moment diagram, it is the point at which the bending moment curve intersects with the zero line.
There can be more than one point of contraflexure in a beam.