A very interesting question!

First, let's address what centrifugal force is. First, consider a situation in which you (the observer) are rotating. This could be a child on a merry-go-round, or someone standing on a spinning planet, or the perspective of a planet going around the Sun, or a car going around a bend in the road, or whatever. When you're in a situation like this, you feel like there's something pulling you outwards. From your perspective, you're going in a circle, and somethings trying to pull you out of the circle, so we call that thing a force, centrifugal force. But here's the funny thing: there's no object causing that force. You can't point to any object in the universe and say that it's causing that centrifugal force; it's purely a consequence of thinking that you're moving in a circle. So we call centrifugal force a 'fictitious force', meaning it's not real, it's a trick of perspective.

Newton's laws tell us that, in the absence of an outside force, things keeping moving in straight lines. If you want to move in a circle, you need a force, which can pull you out of a straight line and into a curve. But if that force stops, you go back to traveling in a straight line, so that force has to be constantly acting on you; we call this the centripetal force. The centripetal force always points in towards the center of the circle, completely opposite to the centrifugal force which pulls outwards. The centripetal force is a real force, with a cause: if you're a planet orbiting a star it's gravity, if you're a car on the road it's friction, if you're a spinning figure skater it's the tension holding your body together. But there is no corresponding source of centrifugal forces, so those are fictitious, or not real.

But we can feel centrifugal force, right, with our bodies (for example, cornering quickly in a car)? So how that be a trick? The key is that centrifugal force pops up when you think you're going in a circle. Your body, subject to Newton's laws, wants to keep going in a straight line. The force to pull you into a circle is coming from friction with your seat, which pulls you towards the center of the circle. In your head, you know that you're supposed to be moving in a circle, so you don't think of the seat as pulling you into the turn, you feel like your body is being pulled outwards. It's that expectation, that perspective, that tricks you into thinking there's a force acting on your body.