Small l libertarians? Almost nothing. Joseph Dejacque, the person who coined the term is generally considered anarcho-communist. And criminally unknown.

Big L Libertarians are just cosplayers. If you advocate against big government but not big businesses. Are you really libertarian? No. They hold the disproven belief that the market will regulate itself in absence of government. Government got into regulation of business because they didn't and can't. They both metastasize into calcified structures of power focused on maintaining themselves. Over the good of the people.

Anarchists believe in no hierarchies while Libertarians believe in no governments but see no issues with power imbalances between people is the basic difference.

Libertarians have money.