Just to chime in, @xokia I'm also having a hard time with the terminology and how it implies what the function will actually be.
So far IF I'm understanding things correctly
the cache drive is used to separate shares from the array because anytime data is written to the array parity will slow things down (doing the parity while also writing) + (this assumes you have parity in place).
because the drive is not slowed down by the nature of parity This allows us to take advantage of the non parity writing/reading in combination of an assumed SSD or nVME drive to also utilize this physical drive for reading/writing/storage of data types that we would feel the most (appdata/vms)
at the same time, the "cache" function of a share that is located on this physical drive can, in fact, function as a true "cache" when set up in a way that incoming data from outside the server will written to this share first (as it should be the fastest write speeds) and then at a later time be "Move/ed" to the array. By the time Mover is doing it's thing we humans would presumably not be affected by this slower speed moving because we've already "moved" on with our lives. I'm not yet 100% sure on how to do this.
Please let me know if I'm wrong on any of these points?
I wanted to lay this out as I've been having a hard time finding all this contextual data in any one place. And I want to avoiding going down one path type and then later realizing that I should have started off in a different manner. So piecing this all together has been a bit of a struggle.