Here is a text book definition. On tv, fox news is conservative, MSNBC is liberal. Being either is a matter of principles, with a variety of interpretations. For example, I am a liberal, but am also pro life (usually a conservative trait).
Liberal vs Conservative
[1] Liberalism is a standing argument between classical liberals and modern liberals, who are usually called conservatives and liberals, respectively.
[2] All liberals share a common set of values; liberals believe in the rule of law, individual rights, democracy, the division of powers, the relative freedom and equality of individuals and free markets. What liberals bitterly disagree upon, however, is the interpretation of these beliefs.
[3] Liberalism represents the center of the political spectrum. Unlike libertarianism, socialism, fascism, and communism, liberalism is not an ideology.
[4] The differences between liberals (i.e. conservatives and modern liberals) may be summarized as follows:
Conservative
1. Natural law
2. Established institutions
3. Liberty over equality
4. Suspicion of power
5. Exceptionalism
6. Individualism
Liberal
1. Positive law
2. Progress
3. Equality over liberty
4. Benevolent government
5. Human Perfectibility
6. Community
[5] Moderate liberals ("centrists") tend to either agree with different principles from each of the two strains of liberalism, or to remain flexible in their preferences to accommodate changing circumstances.