Theory:

Two objects are said to be congruent if they have the same shape and size. Congruence things are exact copies of one another.
In other words, when two or more objects match precisely with each other, then the objects are said to be congruent.
 
red_apples.png
 
In here, the apples \(A\) and \(B\), despite differing in position, look exactly the same. Hence, they are congruent.
Example:
Let us see some day-to-day life congruences:
 
1. Biscuits of the same pack.
 
2. Pages in the textbook.
 
3. Pair of postal stamps of same denominations.
 
4. Two coins of the same dimension and same value.
Important!
Can we check the congruence of two objects or figures?
 
To know that two figures are congruent to each other, one can use the superposition principle. In this method, one can obtain the trace-figure of one of the objects and place the trace-figure on the other object. If the trace-figure and the object match with each other, then the two objects are said to be congruent to each other.
 
The sheet containing the trace-figure can be rotated until it matches the other object. But, it cannot be cut or bent in order to match with the other object.