Definition
Prefix notation, also known as Polish notation, is a way of writing mathematical expressions where the operator comes *before* the operands. For example, instead of writing 2 + 3, you'd write + 2 3. It removes the need for parentheses because the order of operations is always clear. Think of it as a 'command first, then what to do it to' instruction. It's often used in computer science for its simplicity in parsing.