Non-volatile Memory Express is a protocol for accessing data on PCIe solid state drives (SSDs) - drives which retain memory after being powered down. NVMes can support thousands of command queues whereas a simple SCSI drive that uses a spinning disc can only run one command at a time. PCI Express (Peripheral Component Interconnect Express) slots on PCs allow for connections to high speed component.
NVMe is a protocol that manages the PCIe interface. It is the protocol that will allow the fastest access to SSDs.
See more on NVMe technology in the Tip of the Night for February 15, 2021.