I think the best way to put it is that a leftist is someone who believes that workers should own the wealth that they create, while a liberal is someone believes in "socially progressive causes" without examining the underlying systems that bring about the necessity of "socially progressive causes".

For example, a liberal would want more woman CEOs, while a leftist would want to get rid of CEOs.

Both Classical Liberalism and Neoliberalism are at their core capitalist ideologies. While the Republican party is more conservative in both social and economic issues, both parties still operate within the framework of neoliberalism.

In America we only have the Democrat and Republican Parties which are usually labeled as Liberal and Conservative respectively. Since the Democratic party is relatively left of the Republican party, we see the conflation of the label Liberal and Left in American politics. But that's not really accurate when looking at the Ideologies of the parties.

There is Social Democracy, which is still a capitalist ideology where some of the profits are redirected towards social welfare. This is more common in Western Europe and will still rachet towards Fascism.

Leftist ideologies, such as Socialism and Anarchism are fundamentally anti-capitalist, unlike liberalism and neoliberalism. Richard Wolff explains socialism and capitalism very well.

On Liberalism:

What is neoliberalism? A political scientist explains the use and evolution of the term

Liberalism and Neoliberalism

How the Democrats Traded the New Deal for Neoliberalism

On Leftist ideologies:

Noam Chomsky on Anarchism, Communism and Revolutions

Capitalism, Global Poverty, and the Case for Democratic Socialism

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.

Liberals view the status quo (the underlying mechanisms of the government, economy and society) as sacrosanct, legitimate, that it just needs to and will allow itself to be tweaked a bit, that the rules must be followed lest we collapse into chaos.

Leftists view the status quo as widely illegitimate, that a vast multitude of the rules which society operates by are contemptible and functionally evil, and are willing to break the rules to meaningfully change society, that often the entire point is that breaking rules is the only way to establish newer and more just ones.

...

Liberals view Leftists as an extreme part of their fold because they often have similar goals.

Leftists view Liberals as often sharing goals, but as ultimately delusional, magical-thinking self righteous fools, as their methods of achieving these often similar goals are laughably naive, impotent and ineffective, thus functionally making them into conservatives.

It gets even more confusing when you consider anti-capitalist classical liberals

https://www.ellerman.org/wp-content/uploads/2018/12/Classical-Liberal-JurisprudenceJune2018.pdf

@politicalmemes

You can pretty much boil it down to Liberalism is capitalist, leftism isn’t (although where the line is depends who you ask and how left they are).

The confusion mostly comes from from conservative neoliberals lumping social liberals in with the left, even though they’re only separated by a philosophical debate on what “individual freedoms” are and if they’re more important than a completely unregulated economy or not.

Conservatives want us to go backwards. Liberals want us to stay the same Leftists want us to go forward