what can you do with a PCI Express x4 slot?

PCIe x4 Gen2 x4 slot They include hot-swappable SATA 6 Gbps HDDSSD, dual RJ45 LAN ports, a PCIe Gen 3 x4 slot, and two USB Gen 1 (5 x4d slot Lightning Fast Game experience: PCIe slot, Lightning Gen 4 x4 , USB Gen 2x2; Premium Thermal Solution: Extended Heatsink Design and Shield

aauto slot slot specifications: The left slot supports PCIe Gen 4 x4 SSDs, while the right slot supports only PCIe