The mirror formula is \boldsymbol {\frac{1}{f} = \frac{1}{v} + \frac{1}{u}}, where \boldsymbol {f}} is the focal length, \boldsymbol {v} is the image distance, and \boldsymbol {u} is the object distance. It is used to calculate the position and nature of the image formed by concave and convex mirrors.