A rectangle is a 4-sided flat shape made of straight sides, where all four of it's interior angles are 90°.

From these simple facts, it is not hard to work out these related facts:

Opposite sides are parallel.

The sides with a single arrow are parallel to each other.

The sides with double arrows are parallel to each other.

Opposite sides are equal.

The sides with a single dash are equal in length to each other.

The sides with a double dash are equal in length to each other.

There are 2 lines of symmetry.