What do you mean by corresponding parts of congruent triangle

Answer: Triangle is a polygon comprising three angles formed by three-line segments. Two triangles are congruent when their lengths of sides are the same and their angles also measure identical. Therefore, both the triangles are ready to be superimposed from angle to angle as well as side to side.

As we notice in the picture above, ∆ABC and ∆PQR appear to be congruent triangles. This tells us that the corresponding vertices are same, i.e., ∠A = ∠P, ∠Q = ∠B, ∠C = ∠R. Also their sides measure same (AB = PQ, BC = QR, PR = AC). 

CPCT is the abbreviation used to denote corresponding parts of any congruent triangles. It says that if more than one triangle is proved to be congruent, then each of their complementary sides and angles are also congruent.