Operators operate on operands.

Stated differently, operands are the things that are operated on by operators.

For example, in the following expression, the plus character is an operator while x and y are operands.

x + y

Assuming that x and y are numeric variables, this expression produces the sum of the values stored in the two variables.

The variable x would be called the left operand and the variable y would be called the right operand.