Numerical expression is a mathematical equation that contains only numbers and operation symbols. It contains no variables, which are unknown numbers that are often expressed as letters, such as x or y.
In math, there are two types of equations: those with variables and those without variables. An equation with variables is an algebraic expression, such as x - 5 = 2. When an equation does not have variables, it is a numerical expression, such as 7 - 5 = 2. These are both essentially the same equation, but one is a numerical expression, and the other is an algebraic expression.