Glad you asked.
Leftist are those for progressive agendas like social equality and justice, in the tradition of Socialist or Communist ideologies. Liberalism on the other hand is more about individualism and personal liberty, as best embodied by classical Liberals like John Locke or Adam Smith.
In general, Left-leaning people would propose a “great leap forward” to create change through government policies and programs while Liberals tend to advocate for gradual change through the workings of society without government intervention, but don’t dismiss either side! A lot of important work has been done by both sides that deserve respect and recognition. The last thing we need is talking past each other before finding common ground!