Congruences are a concept in mathematics that describe when two numbers give the same remainder when divided by a third number. For example, if we say that 7 is congruent to 3 modulo 4, it means both 7 and 3 leave a remainder of 3 when divided by 4. This is often written as 7 ≡ 3 (mod 4). In geometry, congruence refers to figures that have the same shape and size. Two geometric shapes are congruent if one can be transformed into the other through rotations, translations, or reflections. For instance, two triangles are congruent if their corresponding sides and angles are equal.