The creator, gingerbill, uses it to build real time flame and smoke rendering [0]. AFAIK they have vectors and matrices built into the stdlib as well as various graphics apis[1].
So I'd say from what I know the niche is "batteries included high performance code that can target the gpu"
Odin is a general purpose language, in the same way C.
Professionally, we use Odin to create all of our software at JangaFX: EmberGen, LiquiGen, and GeoGen.
Many people have been using Odin for similar purposes:
* game development
* application development
* 3D graphics
* physics related stuff
* etc
This is what a lot of people feel Odin's "niche" is, even if it is not restricted to that. A good example of this is Odin's first class features for array-programming, swizzling, matrices, quaternions, and many other things useful when dealing with 3D related things (graphics, physics, games, etc).
So I'd say from what I know the niche is "batteries included high performance code that can target the gpu"
[0]https://jangafx.com/software/embergen/
[1]https://odin-lang.org/news/major-graphics-apis/