Liberalism is a political philosophy that classically strifes for as much freedom for the invidual as possible without limiting other's freedoms, separation of church and state, small governments, and free markets without government interference. In theory it can both be left or right in politics, but in my experience they're globally more right leaning (probably due to the small government and free market ideas, which can ultimately lead to ladder pulling tendencies). It is only called leftism in the US because the conservatives are even more to the right, globally US liberals would be seen as right-wing with some exceptions.