It is easy. It all depends where you put the operator.
Prefix +, 2, 2
Infix 2, +, 2
Postfix 2, 2, +
People like Infix because it is the way they were taught arithmetic. Two PLUS Two EQUALS Four.
But Postfix works best on calculators and computers. You just need to master the idea of a “Stack” and pushing numbers onto the stack and popping them off the stack.
Clear now?
Packing the stack make repetitive operations (like in an equation) much faster.