A variable is an important concept of algebra. Both sides of an equation are expressions. Algebraic terms consist of variables coefficients exponents and constants.
Both sides of an equation are expressions.
In simple words equations mean equality ie. An equation obtained by equating to zero a sum of a finite number of terms each one of which is a product of positive integral powers including the zero power of the variables. Both sides of an equation are expressions. So 3ab means to multiply 3 by ab Here is an example of expanding using variables a b and c instead of numbers.