Whats the difference between a simple equation and a linear equation?

In mathematics, an equation is an equality containing one or more variables. Solving the equation consists of determining which values of the variables make the equality true. In this situation, variables are also known as unknowns and the values which satisfy the equality are known as solutions.

The simple equation contains only one variable whose degree (or you can say power) is 1.

For example,  z += 20 , 5(2a + 1) = 100

Linear equation:

A linear equation is an algebraic equation in which each term is either a constant or the product of a constant and the first power of a single variable. Linear equations can have one or more variables

A general form of a linear equation in the two variables x and y is

y= mx +b.