Picture a long length of heavy cord, say 100 feet or longer. Every two or three feet along its length is a swivel with a short drop line and baited hook. These are usually called the stagings. Thus, a trotline might have anywhere from 20 to 50 hooks or more.
That's just the very basics, and there are lots ofl ways to employ trotlines. I usually tied one end to the bank and had a large weight holding the other end down out in the channel.
I think before anyone tries using trotlines, they should get some hands-on lessons with someone experienced. Trotlines have a potential for being dangerous.