Democratic Primaries

They're also not mutually exclusive. "Moderate" Democrats like Biden, Klobuchar, and Buttigieg are also liberals. Some consider one or more of them to be progressives. They're just more moderate than Democrats like Elizabeth Warren. The only true moderates in the party are people like Joe Manchin, and we still have more in common with him than we do with the vast majority of conservatives.

To many, the terms liberal and progressive are relatively synonymous, though some will object vehemently to that characterization. Some see the difference as liberals being more in favor of equality and diversity, while progressives are more interested in changing the status quo (hence, progress).

Sometimes, the issues are the same, but the perceived causes are where the differences reside. This campaign, for example. Biden and others see the GOP as the common enemy, as well as sexism, racism, etc., being factors in inquality. Sanders sees the "establishment" as the main problem, including the GOP and a significant number of Democrats, as well as the media, rich people, and corporations. They're all factors, but how one sees them in relation to each other is often the difference.