I assume that you are asking about liberalism in the historical sense as opposed to liberalism in the context of the American conservative-liberal political divide.
If so, the major value associated with liberalism is the idea that individuals are important and that they have rights that the government must protect. This value informs the most important aspects of liberal systems. For example, one major aspect of a liberal system is a limited government. Liberals believe that government must be limited so that it cannot trample the rights of its citizens. As another example, liberals believe in the sanctity of private property. Again, this is a case in which they believe the government must respect and protect a particular right that its citizens have.
In this way, the most important aspects of a liberal system go back to one value; the idea that individuals and their rights are important.