There are lots of things I don't understand, for example, Algebraic Geometry. Of course I never bash Algebraic Geometry, unlike my relation with Libertarianism. The Stoat has frequently accused me of not understanding Libertarianism, and to be honest, I have devoted less effort to that than Algebraic Geometry. I have however, read the political platform of the American Libertarian Party, the Cato Institute's summary of Libertarian principles, Hayek on how labor unions were responsible for Hitler, Mussolini, and Stalin, and portions of the Wikipedia article on Libertarianism, from which I will quote:
Some libertarians advocate laissez-faire capitalism and strong private property rights, such as in land, infrastructure, and natural resources. Others, notably libertarian socialists, seek to abolish capitalism and private ownership of the means of production in favor of their common or cooperative ownership and management, viewing private property as a barrier to freedom and liberty. An additional line of division is between minarchists (libertarians) and anarchists. While minarchists think that a minimal centralized government is necessary, anarchists and anarcho-capitalists propose to completely eliminate the state.
...which pretty much clarifies everything.
That's a bit too amorphous a beast to provide a good punching bag, so I prefer to concentrate on Libertarianism as embodied in the program of the American right of the Cato Institute, the Libertarian Party, elements of the modern Republican Party, and especially the machinations of the Kochtopus.
Here are two quotes from the Libertarian Party platform:
All persons are entitled to keep the fruits of their labor. We call for the repeal of the income tax, the abolishment of the Internal Revenue Service and all federal programs and services not required under the U.S. Constitution. We oppose any legal requirements forcing employers to serve as tax collectors ...
Libertarians want all members of society to have abundant opportunities to achieve economic success. A free and competitive market allocates resources in the most efficient manner. Each person has the right to offer goods and services to others on the free market. The only proper role of government in the economic realm is to protect property rights, adjudicate disputes, and provide a legal framework in which voluntary trade is protected. All efforts by government to redistribute wealth, or to control or manage trade, are improper in a free society.
Of course they don't explain how governments will function without a tax base.