Spherical mirrors are small pieces of mirrors with coating on one side of the mirror so that light gets reflected back from the surface. A spherical mirror is in the shape of spherical surface, but part of of the total sphere.
A spherical surface can be concave or convex. A concave mirror reflects rays coming from far away to converge on a screen located at its focal point. A real image of the objects at a distance can be displayed on a screen.
A convex mirror reflects rays of light in a diverging manner and so the image of objects at a distance, appear as a virtual image behind the mirror. The virtual image is formed, for example, like in our bathroom mirror, but smaller in size.
Uses of convex mirror are that they are used in rear view mirrors of motorcycles, cars and other places to view happenings behind us.
Concave mirrors are used to reflect light rays like a dentist uses it to focus light on inside of our mouth and see the health of our gums, tongue throat etc..