Question

what is radio drama?

Answer 1

It is drama done over the radio, so everything must be conveyed through sound -- there are no visuals.

Before the advent of television, there were many radio dramas that people tuned into weekly. Some of the early TV shows were those same dramas, transferred to the (at that time) new medium. The famous "War of the Worlds" -- the martian invasion that many people, tuning in late, thought was real -- was done as a radio drama. The radio show "A Prairie Home Companion" still puts on little skits every week that I guess would fall into this category, though they're not really dramas.