The term "2D shapes" refers to two-dimensional shapes. These are shapes that have area, but they do not have any particular measurable thickness associated with them.
Two-dimensional shapes have no thickness, but they do have two measures of distance associated with them, such as width and height. They can be drawn on a flat surface. The dimensions of a two-dimensional shape are used to derive or calculate the object's area. Because two-dimensional shapes have no thickness or depth, there is no notion of volume associated with them. Some examples of two-dimensional shapes are rectangles, circles, triangles, hexagons, trapezoids and quadrilaterals.