Yeah, so I've noticed. There's a lot of Libertarians who are nothing more than crypto anarcho-capitalists.
"Free Market" in general refers to a market place in which people are free to engage in commerce with the government acting primarily as referee and to enforce contracts. A part a lot of people often misunderstand is the "free to engage in in commerce" bit of that, as while MOST inhibition to engage in commerce comes from government regulations (and thus why most discussion about free markets tend to center around it), the government is not the ONLY one that can make it impossible to be free to engage in commerce. Corporations can too, visa via monopoly or anti-competitive actions, and thus the government actually does have a responsibility to keep an eye on such things and break up monopolies or take actions to prevent anti-competitive actions. Another aspect of this kind of thing is truth in advertising laws, as free commerce demands honest assessments by everyone involved, and a person or business that is lying to their customer is inherently NOT engaged in the free market.
Anarcho-capitalism, however, defines "free market" as the idea that anything goes, and that reputation and competition will force the corporations to act fairly and honestly. It's a utopia ideology just as divorced from accurate understanding of human nature as communism is. Many libertarians are also utopianists with their ideology, and tend to fall to the trap of taking their ideals to the extreme, which results in anarcho-capitalism. However, unlike communism and socialism, which have unfortunately high support among modern western populations and considerable support among the media and academic classes and sympathy from major segments of the western left, anarcho-capitalism is an extremist position with little real support. It is mainly used by the progressive left to demonize the right wing position on markets as being more extreme than it is, and it is unfortunately common for libertarians who are loud and disproportionate to also make it seem that this ideal is much more common on the right than it is.