Why are For/While/Do loops used in programs?

Noob here. I understand what they do, I understand the difference between them, but I'm struggling to understand their purpose within a possible program other than doing math.

I'm learning the fundamentals but I don't wanna move on from something unless I truly understand it. And I'm struggling to understand the role loops have in programming from a mechanism point of view within a large program.

Like "if/else" functions make complete sense. Logic like || and && make sense. I can see how that is used within a large program. But what about Loops? What is the main role Loops play if you were to create a large program? Not just a tiny C++ project like a calculator.