AutoZone is a chain, so if you've seen one you know what they're like. Lots of parts and supplies for your car, great prices. Good place to pick up oil or wiper blades, etc. If you do your own repairs this is a good place to get the parts cheaply and reliably.
In my case I don't do my own repairs. I know almost nothing about cars. I was having problems with mine, was about to go on a long trip (PA -> MA), it was 8pm, and my car was overheating. I stopped in to see if they had any suggestions. The counter staff referred me to a guy who ended up being a mechanic. He checked out my car, which ended up needing a new radiator. We went back inside, I got the part, and he installed it. A couple of hours later I was on my way.
Significantly cheaper than if I'd gone to a regular garage, but definitely a bit sketchy. It wasn't made clear to me until after the repair that the mechanic wasn't an AutoZone employee (implication when I was directed to him was that he was). I eventually discovered that he was more of an unofficial freelancer who happened to work out of his van there on occasion.
PROS: cheap, friendly, good selection
CONS: bit sketchy experience that worked out