Libertarianism in the US sometimes (most prominently even, with the Libertarian Party) refers to fully deregulated etc capitalism but more generally means something more like anarchism, a left wing ideology.
Anarchocapitalism is an oxymoron and anarchists do not count it as anarchism.
5ier: Its the idea that the personalized power of both economic and social rulers should be minimized. Neither inheriting a factory nor inheriting a title of nobility should give you power over me.