From https://en.wikipedia.org/wiki/Left-wing_politics:

Left-wing politics describes the range of political ideologies that support and seek to achieve social equality and egalitarianism, often in opposition to social hierarchy as a whole or certain social hierarchies.

…

In modern politics, the term Left typically applies to ideologies and movements to the left of classical liberalism, supporting some degree of democracy in the economic sphere. Today, ideologies such as social liberalism and social democracy are considered to be centre-left, while the Left is typically reserved for movements more critical of capitalism, including the labour movement, socialism, anarchism, communism, Marxism and syndicalism

https://en.wikipedia.org/wiki/Liberalism

Liberalism is a political and moral philosophy based on the rights of the individual, liberty, consent of the governed, political equality, right to private property and equality before the law. Liberals espouse various and often mutually warring views depending on their understanding of these principles but generally support private property, market economies, individual rights (including civil rights and human rights), liberal democracy, secularism, rule of law, economic and political freedom, freedom of speech, freedom of the press, freedom of assembly, and freedom of religion.

(Emphasis added)

Basically, liberals care more about equality of opportunity, while leftists care more about equality of outcome. (And, of course, conservatives actively oppose equality and promote hierarchy.)

On a “political compass,” leftism is the left half (obviously). Liberalism is a fuzzy blob centered somewhere below and right of center, but big enough to extend at least a little ways into the other quadrants because of how many different kinds of “liberalism” there are.