The arithmetic operators (+,–,*,/) are called binary operators because they require two operands:one operand on each side of the operator.
For example:
5  3
In that example...

5 and 3 are the operands

"" is the binary operator
The (–) operator is also used to negate a number (like –5). In this case, –5 is called a unary operator, because it has only one operand.