An expression in which operators follow the operands is known as postfix expression. The main benefit of this form is that there is no need to group sub-expressions in parentheses or to consider operator precedence.

The expression “a + b” will be represented as “ab+” in postfix notation.

A postfix expression, also known as a postfix notation or reverse Polish notation (RPN), is a mathematical notation in which every operator follows all of its operands. In other words, the operator is placed after its operands.

For example, the infix expression “3 + 4” would be written in postfix notation as “3 4 +”.

Postfix notation has the advantage of being unambiguous and not requiring parentheses to specify the order of operations. It is often used in computer science and calculators for arithmetic expression evaluation because it can be easily processed using a stack data structure.