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

NVME PCIE SSDs Solid State Drives nvme m 2 slot There are two types of SSDs: SATA and NVMe SATA uses an older interface with one designed around hard drives while NVMe is designed for flash memory nvme slot types If you cannot see the connected SSD or NVMe drive in Windows Explorer or Disk Management, there might be some fault with the storage drive

nvme slot vs m2 PCIe To Adapter Board for Raspberry Pi 5, Compatible with 2280 2260 2242 2230 size NVMe Protocol SSD, 8Gbps Data Rate,