Reverse Polish Notation (RPN) is a mathematical notation in which operators follow their operands, eliminating the need for parentheses to define calculation order. Instead of writing expressions like (3 + 4) × 5, in RPN you would write 3 4 + 5 ×. This method uses a stack-based approach, where numbers are pushed onto a stack and operations are performed on the most recent entries. RPN is favored in some calculators and computing systems because it simplifies the process of evaluating complex expressions and reduces ambiguity, making calculations faster and less error-prone.