It kind of has a double meaning. One side is someone who believes in like democracy, freedom, human rights, and the other side is someone who believes in private property. For historical reasons, the two tendencies are like joined together on most things, but there are differences.

A lot of leftists don’t like liberals because they defend private property and capitalism, but a lot of liberals see themselves as leftists because of those progressive values.

Whether or not a liberal is left wing very much depends on the liberal. Every socialist was once a liberal, whether they were political or not. Conservatives are a kind of liberal, but with the progressive parts removed so it only defends private property.

capitalism is really good at like hiding away its injustice behind contracts and laws, a socialist would see those laws as unjust and want to do radical reforms up to and including overthrow of the ruling billionaires. a liberal might not see the injustice, or if they do, tend to want to stick to courts and reforms because it does contain elements of fairness and justice. liberal justice is more fair than feudal justice, but less than what many socialists would like.

The meme is a reference to the idea that social democracy, liberalism and fascism are all different aspects of capitalism.