Help with Prions?!

So I'm doing microbiology and we're going over the structure and replication of prions(scrapie) and I've found it so confusing. I dont know if it's just the way my teacher has gone over it or if it's generally just a confusing topic. My understanding is that they're misfolded infectious proteins which contain no genome. How do they go on to then replicate? Our teacher has dedicated one slide to it which doesn't make much sense at all. I can post a picture of the slide to show you what I'm working with but I would appreciate any help. We have to be able to explain their structure and go on to say how they replicate.

Prions do not replicate per se. Prion protein (PrP) is found in the cell membrane as PrP^c. Prion diseases occur when PrP^c become misfolded forming the infectious prion particle (PrP^Sc). PrP^Sc can then cause other PrP^c particles to become misfolded, producing more PrP^Sc particles.

So we naturally have PrPc but when exposed to PrPSc, it goes on to change other PrPc into PrPSc? What differentiates the structure of a pathogenic prion protein from a non pathogenic prion protein?