How do people randomly find and follow you on Twitter?

[Mlek Booth]

I get that people follow to promote themselves, but how did they find me? Is it from retweeting things? That's all I can think of, since I'm very, very noob at this. And let me tell you, they are really random, like random types of people, but they seem legit (not phishes/scams etc).. or maybe they are lol.

Yeah, new to this thing as you can tell. Thanks.