ΔABC ≅ ΔEFD
Two triangles are congruent if pairs of corresponding sides and corresponding angles are equal.
If we write ΔABC ≅ ΔEFD, it would mean that,
Correspondence between vertices:
A ↔ E, B ↔ F, C ↔ D
Correspondence between sides:
AB = EF, BC = FD, CA = DE
Correspondence between angles:
∠A = ∠E, ∠B = ∠F, ∠C = ∠D