Question: what are these? And how do you notate them in musescore?

I don't know how to describe it in the subject heading. I'm sure we went over this in one or more music classes I had back in college. But most of the music I perform doesn't have this so I didn't really retain that info.

So, yes, I'd like to know what type of notation this is. And if musescore can even notate it.