Congruent figureS 
    Figures having same shape and size are called congruent figures. 
    Two figures are congruent if each is an exact image of the other. E.g. coins of M5.

Concept of superimposition 
    If two figures are congruent, then without bending or changing their position, if one figure is placed over the other figure and they completely overlap each other, then two figures are said to be superimposed on each other. 

  •     Two figures are congruent if one figure superimposes the other figure.

If triangle T1 superimposes triangle T2 and these two figures exactly cover each other, then they are called congruent. This method is also called superimposition method.