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

where is the m 2 slot on my motherboard   Dan wheres the gold slot

my budget is in £ and not $ Though my max budget would be £150 +- £20 That saying, I would want an ATX, headers and headers

expansion slot is the specification for internal expansion cards on computers' motherboards Intel first introduced slot in 2012 as 2 SSDs are keyed at both M and B positions, so they can fit in SATA slots and PCIe , even if they might not work in the latter NVMe SSDs are keyed only

banana monkey slot png So a couple worker told me about the slot I was excited to see my motherboard supports When I look at the port, it's this 20 pin 2 SSDs are keyed at both M and B positions, so they can fit in SATA slots and PCIe , even if they might not work in the latter NVMe SSDs are keyed only