What do AAS, SSA, SAS and SSS stand for in geometry?

Hint: In the given question we are just asked the full form of the three postulates of geometry that are used to prove the congruence of triangles. Apart from this in order to clarify all these terms in a better way we will define them.

Complete step by step solution:
AAS stands for angle angle side postulate in geometry. This tells us that if two angles and a non-included side of one triangle are congruent to two angles and also the corresponding non-included side of another triangle, then the given two triangles are said to be congruent to each other.
SSA stands for side side angle postulate. In this postulate of congruence, we say that if two sides and an angle not included between them are respectively equal to two sides and an angle of the other triangle then the two triangles are equal.
SAS stands for side angle side. Now, mainly we use these terms in order to show that the triangles are congruent or not. So, in that case if two sides and the angle made by the two sides of the one triangle are congruent to two sides and the angle made by the two sides of the other triangle then we say that the two triangles are congruent to each other.
SSS stands for side side side postulate or SSS postulate. We say that the two triangles are congruent if the three sides of the one triangle and the three sides of another triangle are congruent to each other. It is one of the simplest postulates to check the congruency of the triangles.

Note: Do use the right postulate. Don’t just cram it and apply without actually noticing what kind of triangle is given and what is asked in question. Also check whether some condition to use a specific postulate is given or not.