motherboards with pci slots - pci express - Can I turn a PCI-e x1 slot into an old PCI slot ... slot big win 888

Choice of I/O backplane: PCI-X with 8 available PCI-X slots, or the I/O backplane, containing 4 x8 PCI Express slots, and 4 PCI-X slots.

While older mini ITX motherboards only came with 1 M.2 slots, most current mini ITX motherboards offer 2 to 3 M.2 slots which is definitely quite amazing considering the compact form factor of mini ITX motherboards.

I'm comparing different Micro-ATX motherboards for a home server build and I was wondering what I would use PCI and PCI Express slots for?