The SSS congruence postulate states that if all three sides of one triangle are congruent to the corresponding sides of another triangle, the triangles themselves are congruent. Triangles are congruent if, when one is superimposed on another, they match.
Several ways exist to prove triangles congruent. Aside from the SSS (or side-side-side) method, there are the SAS (side-angle-side), ASA (angle-side-angle), AAS (angle-angle-side) and HL (hypotenuse-leg) postulates. If triangles are congruent by any one of these, they are congruent. Congruent triangles have the same shape and size, though it is possible for one to be a mirror image of the other or rotated in some other way.