Depends on which model. I got one earlier this year with a 7th gen core i5 processor: NUC7i5BNH with a i5-7260U, 2 cores, 4 threads, 15W TDP. Now you can get them with 8th gen core processors like these (among others):

  i5-8259U, 4 cores, 8 threads, 28W TDP
  i7-8559U, 4 cores, 8 threads, 28W TDP
  i7-8705G, 4 cores, 8 threads, 65W package TDP
  i7-8809G, 4 cores, 8 threads, 100W package TDP

The last two have fancy integrated graphics and only come in a larger form factor with a skull on the side.

edit: conciseness, formatting