What is an slot on a motherboard used for?

So, I am using the MSI MPG z390 PRO CARBON AC, and there's some weird thing that has been going on in the bottom slot When using the top

2 drive can still be connected using an adapter card that fits a PCIe slot SATA SSDs SATA drives are becoming an increasingly popular form

slot yaba For example, the ASUS Z97-A lists the slot as Socket 3, with M Key, type 22602280 so it supports drives that are 22mm wide and

slot machine addiction slot connections , 1s Smax f1 , under the algorithm with functional division of second stage switches if and only if : mm1 + m2 , where fo nfi 2 m1