What are typical use cases of scrextend?

I see this package often loaded but find quick description of the relevance of the package hard to come by.

makes some features of the KOMA-Script classes available for other classes

I had never heard of KOMA-script before, it is not mentioned in any of the three books I have on LaTeX. But I see there is also a package with the name koma-script.

I’m looking for some typical issues koma-script/scrextend use cases. In other words, what likely to break if I remove it?