NVMe stands for Non-volatile Memory Express. While they are not the same, they work together in a sort of way. NVMe is just a protocol for storage used by many high-speed PCIe SSDs. NVMe is often used to refer to PCIe Gen 3 SSDs while the Gen 4 SSDs are referred to by using the PCIe Gen 4 name. This differentiation is not accurate since both of them are NVMe drives on a basic level.