The word 'congruent' means 'exactly equal' in terms of shape and size. Even when we turn, flip, or rotate the shapes, they remain equal. For example, draw two circles of the same radius, then cut them out and place them on one another. We will notice that they will superimpose each other, that is, they will be placed completely over each other.

In Geometry, two or more figures or objects are congruent if they have the same size and shape, usually referring to line segments, shapes/figures, and angles. For example, line segments with the same length are congruent, and angles with the same measure are congruent.

The same shape and size (but we are allowed to flip, slide or turn). In this example the shapes are congruent, we only need to flip one over and move it a little. Angles are congruent when they are the same size (in degrees or radians). Sides are congruent when they are the same length.