Libertarianism is a political philosophy that has been in development since Adam Smith. The most basic definition of the idea is "maximum personal and economic freedom at the expense of a limited government". There are 3 kinds of libertarianism: left-libertarianism, anarcho-capitalism, and moderate libertarians. Libertarianism shares characteristics with conservatism and liberalism but is not one or the other, for instance, libertarians believe like conservatives in limited government, religious freedom, right to bear arms, and in capitalism. Similarly with liberalism libertarians believe that equality under the law, drug decriminalization, and ending surveillance.
Now let us break down what libertarians believe issue by issue.
For economic issues libertarians strongly believe in capitalism. Capitalism is the basic idea of "If you give me a good or service in exchange I will give you money". For them, the ideal form of capitalism is called laissez-faire capitalism which basically means the government has absolutely no business in making regulations on the private sector, seizing property, or setting prices of any kind. Now I did mention earlier that there are left-libertarians. From a philosophical standpoint, you cannot be a small government freedom loving person if you believe in left-wing economics (socialism/communism). These kinds of systems require a large over-reaching government to enforce its economic ideas on its citizens which always lead to authoritarianism.
For issues regarding sociology, libertarians believe that if you let people do what they want so long as they don't violate the non–aggression principle of not harming a fellow human. For things like drugs, most of them have the idea that the United States drug war was a pointless campaign that wrongly incarcerated thousands of people for minor offenses. When it comes to abortion libertarians are split on this issue from the one side saying that it is murder, therefore, it violates the NAP, with the other side saying that the government has no right to tell you what you cant do with your body.