Theory:

Two objects are said to be congruence if they have the same shape and same size. Congruence things are exact copies of one another. 
red_apples-w300.png
In here, the apples \(A\) and \(B\) are congruent.
Example:
Let's see some day to day life congruences:
  • Biscuits of the same pack.
  • Pages in the textbook.
  • Pair of postal stamps of same denominations.
  • Two coins of the same dimension and same value.