Trap is characterized by deep, pulsating, hard-hitting sub-bass, 808 drums, sharp synth leads, and Dubstep elements (drum patterns, heavy bass drops, and a focus on low-end frequencies). A lot of the stuff that comes from the shadier section of Equestria (down south). While Trap Rap has some rapping, Trap itself generally does not.
Check out these artists who specialize in this music (or more than likely check out a few of those below)
Feel free to recommend some musicians (those that specialize in it), and tracks not included in here, in the comments section.