CPCT stands for Corresponding Parts of Congruent Triangles.
It means that if any two triangles are congruent by ASA , SAS , RHS , SSS , then, their remaining sides and angles will also be equal.
Example:
If AB = YZ
BC = ZX
AC = YX
∴ Δ ABC Δ YZX ( SSS Congruence criterion )
⇒ angle A = angle Y , angle B = angle Z ,
angle C = angle X ( CPCT )
Hope this helps!!!!!