A parallelogram is a four-sided shape where opposite sides are parallel (they run alongside each other and never meet, like train tracks) and equal in length. If you took a rectangle and pushed on its corners until it leaned to one side, you'd create a parallelogram. Rectangles and squares are actually special types of parallelograms, but when most people say parallelogram, they mean the slanted kind.

Picture a diamond shape that's been stretched sideways, or imagine how the shadow of a rectangular book might look when you tilt it. That's a parallelogram. The opposite sides stay the same length and stay parallel to each other, but the angles at the corners aren't right angles anymore (except in rectangles and squares).

Parallelograms show up more than you might think: in the design of bridges, in tile patterns, in the structure of crystals, and even in how artists create the illusion of depth in drawings. When architects design buildings or engineers plan structures, they often work with parallelogram shapes because of how forces distribute along those parallel sides.