It's essentially a replacement for vertex shaders which map more closely to how GPUs are processing big and complex triangle meshes as small packets of vertices in parallel by doing the job of splitting a complex triangle mesh into such small packets of vertices in an offline asset-pipeline job instead of relying too much on 'hardware magic' like vertex caches.
AFAIK mesh shaders also get rid of (the ever troublesome) geometry shaders and hull shaders, but don't quote me on that :)
By far most traditional triangle rendering use cases should only see minimal performance improvements though, it's very much the definition of 'diminishing returns'.
It's definitely more straightforward and 'elegant' though.
PS: this is a pretty good introduction I think https://gpuopen.com/learn/mesh_shaders/mesh_shaders-from_ver...
Oh, awesome! Yeah, that's a great introduction. Seems like it introduces a new abstraction that allows a single mesh to be mapped to much smaller groups of vertices so you can take advantage of BVHs and stuff like that on a more granular level, right in the shader code. Very cool stuff! Thanks for the info.