NVMe drives come in three physical forms: U.2, M.2, and full sized PCIe.
NVMe drives actually use 4x PCI lanes for their transport. This (usually) means there is no translation in between the CPU and the storage, like you would find in a RAID card.
U.2 drives have a connector that looks like a SAS drive, but it has more gold connectors. This is also called SFF-8639.
M.2 drives have keys, and NVMe drives are usually M keyed. Please note that the motherboard must also have PCI lanes, not SATA lanes, for the NVMe drive to function.
The last variant is the full-sized PCI version. These are the most straightforward, as they plug directly into the slot.
