What do the Intel Xeon Phi's do?

I heard logan or wendel talking about them in their Xeon build video.

I tried searching them up to see if I could get any information. I couldn't really get any other than its a coprocessor.

What exactly does it do?

they do math to solve equations to do processing, same as any processor, i believe the only applications that use them are weather simulations and in super computers, also for reference they're based on cpus not gpus