It is a regular 8 sided octagon
A figure with 4 equal sides and 4 equal angles is a square :)
an equilateral triangle has all its angle and sides equal
a square is a plain figure which has all the sides equal but a rhombus is a plain figure which has the opposite sides equal.
A regular polygon
Perimeter is the measurement of all sides of a figure. For example, if you have a rectangle that has 2 sides of 4 inches long and 2 sides of 8 inches long, the perimeter is the total of all sides, which in this case is 24 inches.
A square is a rectangle with 4 equal sides and 4 equal angles. A rhombus is a parallelogram with 4 equal sides.
It is the side of an isolateral figure.