It’s when they give you money without you putting up anything as a collateral.
In short, if you don’t pay it back they lose it all.
These loans come with high interests.

Sure, it’s where they agree to lend you money, without any kind of backup. Usually, it’s done to people who aren’t very creditworthy, so the rates tend to be higher - a LOT higher - to make up for the extra risk.

If it’s overhead you’re worried about - well, an uninsured personal loan is the MOST expensive way to finance a used car.