There was a sort of evolution in the early-to-late 20th Century
From: Bohemian, to Beatnik, to Hippie.
Bohemians were people who were inclined towards a rather decadent lifestyle. The stereotype has them constantly having "wine and cheese" parties. Like someone else said, their origins were the "literary set" of Paris in the 19th century---especially someone like Charles Baudelaire. They might or might not have had gainful employment. They tended to enjoy sitting around all night having philosophical discussions, and at least some of them also engaged in orgies. They tended to dress "exotically," like perhaps in some sort of Indian (east) garb. Or other sorts of clothes. Woody Guthrie was definitely not a "Bohemian." They weren't into folk music; they were more into classical music.
Beatniks were people who attempted to imitate the "Beat Generation" of Jack Kerouac, Allen Ginsberg, etc. Kerouac, at least, couldn't stand the "Beatniks," and thought they "imitated" the Beats poorly. They tended to have a more blatant disregard for society than the Bohemians, who were rebellious, but more quietl so. Stereotypically, they would hang out "coffee houses" and listen to poetry. They would play bongo drums. Unlike the Bohemians, who tended to speak "intellectually," they tended to speak in the "hip slang" of their times. They were seen as being "dirty" by "straight" people. Maynard G. Krebs was a Beatnik character in a show called "The Many Loves of Dobie Gillis."
Like the Bohemians, they experimented with drugs. Like the Bohemians, the had literary pretentions, and also enjoyed sitting up all night talking about philosophy.