A euphemism is a way to try and make something sound better than it is. For example, you might find an ad for an apartment that says "Cute, cozy apartment just right for one person." And when you get there to look at the apartment you find its cramped, too small for you! Car salesmen are good at using euphemisms too. They will find ways of selling even the worst of cars. Here are some examples:
"Good Runner" usually means its ugly, rusty, noisy or otherwise unattractive
"Sharp" usually means it has some visual appeal despite other flaws
"Babied" means it shows it has been cared for but usually cosmetically, not necessarily mechanically.