What are these markers for?

I got some beautiful stitch markers from my oldest step daughter for Christmas - she’s the one who taught me to knit. I’ve always wanted some - but some are wierd looking & I dont know what they are for.
The ones I’m not sure about are the ones that don’t hook all the way around - not circular - they are like a fancy upside down “U” - anyone know what they are used for?
I’d post a picture to show, but I’ve having trouble getting it to fit…I hope someone knows what I mean.

I believe they’re row markers–you can hook them on the edge to mark a particular row.