The ASRock Fatal1ty Z170 Gaming K6+ comes with three PCI Express 3.0 x16 slots and three PCI Express 2.0 x1 slots. There is also an M.2 slot supporting both PCI Express 3.0 x4 and SATA-600.
The two first PCI Express x16 slots work on x16/x0 and x8/x8 configurations, which means the first slot work at x16 if the second one is unused, but it it is occupied, they will both work at x8. The third PCI Express 3.0 x16 slot works always at x4 speed.
An interesting feature is that the PCI Express x1 slots have open endings, so you can install PCI Express x4 or x16 on them. Of course, they will work only at x1 speed in this case.
The motherboard supports CrossFire with up to three video cards, and SLI with two video cards.