A curved mirror is just a small piece of a sphere — concave curves inward, convex curves outward, and a handful of labelled points describe both.
Concave mirror: parallel rays converge at F, which sits in front of the mirror.
A spherical mirror is a mirror whose reflecting surface is a cut-out piece of a sphere. If the reflecting surface curves inward, like the inside of a spoon, it's called a concave mirror. If it curves outward, like the back of the spoon, it's a convex mirror.
A few labelled points make it possible to talk about these mirrors precisely. The pole (P) is the centre point of the mirror's surface. The centre of curvature (C) is the centre of the sphere the mirror is cut from — note that C is not on the mirror itself, it's out in space in front of (concave) or behind (convex) it. The line running through P and C is the principal axis.
When rays travel parallel to the principal axis and hit the mirror, they all meet at (or appear to come from) one point called the principal focus (F). The distance from the pole to this point is the focal length (f).
There's a simple relationship between these: the radius of curvature is always exactly twice the focal length, written R = 2f. That means the focus always sits exactly midway between the pole and the centre of curvature.
Key exam points
Watch it explained
Common Terms in Spherical Mirrors — Focus, Pole, Centre of Curvature, Focal Length · CBSE Class 10