I’m just getting beyond the basics of UV mapping and I keep coming across these terms. UDIM, UV maps, UV sets. Are there clear differences to each? Are UV maps and UV sets the same thing with different terminology?
I did a bit of research on UDIMs, and it seems the use case for those are primarily for movies more than game dev. Is that correct?
Apologies if this is too broad of a question.
As in anythign else… it’s somekind of mix… sometimes there is some interchanging of terms and i also do not claim to know every “version” 
To map some 3-dimensional object to a 2-dimensional texture (map/image) the 2-dimensional UV-coordinates are stored for every XYZ coordinates of this object. This is the actual mapping but to “see” this the edges between the 3D vertices re-drawn (mapped) on the 2D canvas sometimes is also called UV-map (the left on the image) while in fact is only a reprensation of the (UV) mapping… sometimes also UV-layout
Here the eyes do share the same map and material but the also could use different materials UV-map (imagine one or two big discs for the eyes)… so now you have a set of UV-maps for this object… or UV-set. The big contra is: usually UV’s are located in the (0,0) to (1,1) area so the all do overlap. Some (like blender) can store them "all over the place: so you can make them non-overlapping… but: some interchange formats only store values between 0 and 1…
So including this flaw in interchange formats for large objects this material and map for ever single (sub) part of an object was/is a big hassle.
UDIM where invented (originally for movie FX but also usable in every “big object”) to overcome this:
Imagine a big grid of possible UV maps so now you see the whole set in one big view and even every single tile can be of different size. So you do not have to switch maps. Now every single UV map is “just organized” into this grid and so use values between 0 and 1 but the location in this grid detemines the actual image to use for this mapping.
Ohh and the process to build up the UV-map is sometimes called UV-unwrapping.
