Overlapping triangles refer to a geometric scenario where two or more triangles share a common region or area. This concept is essential in understanding congruence, especially when determining relationships between the angles and sides of the triangles involved. When triangles overlap, their corresponding parts can often be analyzed to prove properties like congruence, similarity, or to apply rules such as the Side-Angle-Side (SAS) or Angle-Side-Angle (ASA) criteria.