Answer:
The solid figure formed is a cylinder.
Explanation:
Rotation is an example of transformation in which a given figure is rotated about a reference point (origin) or line (axis). This converts majorly a two dimensional figure into a three dimensional figure or shape.
When a square is rotated about an axis, either horizontal or vertical, it generates another shape called a cylinder. Therefore, a 2D figure(square) generates a 3D (cylinder) shape due to rotation about an axis.
The cylinder would have circular surfaces with diameter which is the same as the length of the side of the initial square.