Codes?

I'm new to the forum, so I'm wondering what everyone keeps talking about when they say "codes"? I know Bonneville's have a computer in them, I've gotten as far as to figure it's got something to do with that.

You have a "service engine soon" light come on in your car, and you can hook up a code reader and it will tell you a code (which will point to the problem of your car).The dealer will do this for a fee, or you can go to autozone and they will do it for free.You can also buy a code reader which arent too expensive.Older cars can be read with a paperclip, possibly yours if it is 92.It hooks up under your dash , under steering wheel.