Similar triangles are triangles that have the same shape but may differ in size. This means that their corresponding angles are equal, and the lengths of their sides are in proportion. For example, if one triangle has sides of 2, 3, and 4 units, a similar triangle might have sides of 4, 6, and 8 units. To determine if two triangles are similar, you can use the Angle-Angle AA criterion, which states that if two angles of one triangle are equal to two angles of another triangle, the triangles are similar. This property is useful in various fields, including geometry and trigonometry.