Mathematical expressions are a combination of numbers, variables (like x, y, or z), and operators (like +, −, ×, and ÷) that represent a particular value or quantity. For example, 2+3 is a simple mathematical expression. The + is an operator that tells us to add the two numbers together.

The operation "÷" is called division. When we say "20000 ÷ 2", we're asking "how many times can we evenly distribute 2 from 20000?"

More Info: en.wikipedia.org