AVX-512 is not a dedicated sorting instruction set, but rather instructions dedicated to doing the same computations in parallel over 512 bit wide registers. So you can do the same operation in the same time for 8 doubles, 16 integers, or 64 bytes at once.
Coming up with good usage of those instructions can be tricky. It's not just the typical arithmetic things, but also instructions that shuffle around values in those registers based on values elsewhere and combining all that cleverly then can yield speed-ups for algorithms that deal with lots of data serially.
A while ago while trying to understand all that (for the older instruction sets) I've read this CodeProject article: https://www.codeproject.com/Articles/874396/Crunching-Number... – AVX-512 is basically similar, just wider. Although I've heard it has a few more useful instructions as well that have no counterpart in the older instruction sets.