When we were there for the BOD meeting I rode this which I would call it a train. It runs above ground sometime and in DC it seems to be underground kinda like a subway. It is a rail system.
It is a great way to get around see things on your own, but there is a little learning curve, and I wish I had gone to this website for info 1st http://wmata.com/ .
Now here is the really good news…when we were there the Orange Line was the closest station, a 5 mile shuttle ride from the hotel. By the time we get there for the reunion the Silver Line will be finished and the Spring Hill station will be about 300 yds from the hotel. http://silverlinemetro.com/spring-hill/