I visited Chicago just the once, but I used more than one kind of transit, so this might be correct: the El is light rail, equivalent to BART, called that b/c it's ELevated. There are commuter trains that sure do look like real trains, equivalent to Caltrain, which might be the Metra.

(When I rode the commuter train out to visit Bean's aunt etc for dinner, it was *very* different from being at home. Every Single Person was dressed up in business clothes. I was the only person I could see in a black leather jacket. That would *not* be true on BART in downtown SF.)