People tend to use this word as a synonym to "everything bad", but it's not its actual meaning. Fascism is a one of totalitarian ideologies, that has racism in its core. We'll have a separate post for racism, but its idea revolves around the natural superiority of one race over all "others," leading to the belief that all "others" should either be eliminated or enslaved.
Natural superiority means it comes from nature, so once being born you can do abolutely nothing to change it.
Paradoxically, fascism did not originate from uneducated savages, but rather from respectable and intelligent professors.
Yeah, it's a common element in deplorable ideologies. That doesn't mean populism isn't necessary for fascism.