What is an slot on a motherboard used for?

2 SSD ADATA XPG SX8200 PCIe Gen 3x4 2280 built in As I checked there are two to me identical slots, both of these slots

I have my new build with a 13700K i7 and an ASUS z790 motherboard which has 5 m2 slots When I first did the build, I only used 2,

m2 slot mainboard 2 SSD ADATA XPG SX8200 PCIe Gen 3x4 2280 built in As I checked there are two to me identical slots, both of these slots

m2 slot motherboard, lowers the risk of damaging your memory module Besides the onboard LAN port, users may also choose wireless connections by slot