Rectangle
A rectangle is a four-sided flat shape where every corner is a perfect right angle (90 degrees).

               
The Key Rules
Four Sides: It is a closed shape made of straight lines.

Right Angles: All four corners look like the corner of a book or a piece of paper.

Equal Opposite Sides: The sides across from each other are the exact same length.

Examples:
A smartphone screen
A dollar bill
A standard door