It’s a broad term. Basically anyone who wants to weaken/destroy the state might call themselves such. It was popularized thanks to oil oligarchs before they realized they could just make the mainstream neo-liberal and get what they want. The positions that are commonly held by followers can include deregulation, decreasing taxes, gun-rights, increasing free-speech, decreasing oppression for minorities, and decreasing militarism (though some want military to be the only thing the government spends money on).