To quote Rush, "Words mean things." Seems like a good place to start.
Well, here is the introductory description of libertarianism from Encyclopaedia Britannica, let’s start there:
“libertarianism, political philosophy that takes individual liberty to be the primary political value. It may be understood as a form of liberalism, the political philosophy associated with the English philosophers John Locke and John Stuart Mill, the Scottish economist Adam Smith, and the American statesman Thomas Jefferson. Liberalism seeks to define and justify the legitimate powers of government in terms of certain natural or God-given individual rights. These rights include the rights to life, liberty, private property, freedom of speech and association, freedom of worship, government by consent, equality under the law, and moral autonomy (the pursuit of one’s own conception of happiness, or the “good life”). The purpose of government, according to liberals, is to protect these and other individual rights, and in general liberals have contended that government power should be limited to that which is necessary to accomplish this task. Libertarians are classical liberals who strongly emphasize the individual right to liberty. They contend that the scope and powers of government should be constrained so as to allow each individual as much freedom of action as is consistent with a like freedom for everyone else.”
Note that when they say “liberal”, they mean “classical liberalism”, not the modern progressive-Marxist variety that is called liberalism. That’s a whole ‘nother term that people tend to be quite confused about nowadays, if you don’t define it explicitly.