How does the evaluate reverse Polish notation problem use a stack?

Reverse Polish notation, also called postfix notation, places operators after their operands. Process tokens left to right: when a number is encountered, push it onto the stack. When an operator is encountered, pop two operands from the stack, apply the operation with the second popped value as the left operand and the first popped as the right, then push the result. After all tokens are processed, the stack contains exactly one element, which is the final answer. ---