What does the X4 mean in an PCIe Gen X4 NVME drive?

New NVMe ssd in slot issues m 2 nvme slot 2 SSD slot on your motherboard These slots are similar to PCIe expansion slots but are much smaller And this makes them perfect for SSD drives m2 slot types 2 4x4 PCIe card enables you to mount four NVMe PCIe SSDs onto a single x16 card slot—it can transform the way you work With the Sonnet M

m2 nvme slot And i wanted to add an 500 GB SSD NVME Samsung Evo and i am just making sure if i have a slot and if its compatible or not ? Thanks for the