This is a PSA to anyone who has a squeaking dryer. If your dryer is squeaking, get it serviced. I know a lot of us have seen the squeaky dryer trope in movies and on TV, but it's not normal for your dryer to be squeaking. The part that I've seen cause squeaking most often is called the idler pulley, and I'm going to give you a little visual on how that works, and why it's so important.
Let's pretend this rectangle is your dryer, this circle is your drum, that's where you put your clothes. This square is your motor, and this square is your heater, or your burner if you have a gas dryer. And this little dude is your idler pulley. Your motor has a column in the center that rotates. The orange thing, which is your belt, makes contact with the drum and the motor, so the motor can turn the belt and turn the drum.
But when it's wrapped around just the motor and the drum, the belt is a little too loose to do that. So the belt gets wrapped around the idler pulley as well to put tension on it. This means that when the motor and the idler pulley are turning, the drum is, too. Right here, there's a wheel with a bearing inside the idler pulley that lets everything turn smoothly. And when that bearing starts to fail, you guessed it, it starts to squeak. And if the bearing breaks, the wheel can snap, which takes the tension off the entire thing, and it won't turn. I can't guarantee that that's what's squeaking, but that's the most likely culprit.