A square has four equal sides and four equal angles (90 degree angles or right angles). A rectangle is a quadrilateral with 4 right angles. It is similar to square except that its sides are not equal.
Square
Perimeter of Square
Perimeter of the square is 4 times the length of the side. For a square of length L, perimeter = 4 * L
Area of Square
Area of square is the square of length of the side. Area = L * L
Properties of Square

The diagonals of a square bisect each other and meet at right angles (90 degrees)

The diagonals of a square bisect its angles

The diagonals of a square are perpendicular

Opposite sides of a square are both parallel and equal in length

All four angles of a square are equal. (every angle of a square is a right angle)

The diagonals of a square are equal.
Rectangle
A rectangle is a quadrilateral with 4 right angles. It is similar to square except that its sides are not equal.
Perimeter of Rectangle
Perimeter of the rectangle is sum of the length of its sides. Perimeter = 2 * (Length + Breadth)
Area of Rectangle
Area of rectangle is multiplication of its length and breadth. Area = Length * Breadth
Properties of Rectangle

All angles are right angles (90 degrees)

Opposite sides are parallel and equal.

Diagonals bisect each other.