What do you understand by dimensional formula and dimensional equation?

Dimensional formula of a physical quantity is an expression which tells us:
 
i) the fundamental units on which the quantity depends on, and 
ii) the nature of dependence. 

For example, dimensional formula of area is [M⁰L²T⁰].

This expression tells us that area does not depend upon mass and time but unit of length is required twice. 

Dimensional equation: Physical quantity whebn equated with dimensional formula becomes dimensional equation. 

i.e. dimensional equation of area will be given as,
                          A = [M⁰L²T⁰]