Non-Volatile Memory Express is a little drive about the size of a stick of gum, or smaller ones a little less than a half of stick. This memory module connects directly into the motherboard, and uses the faster PCI-X bus rather than the SATA bus. The largest NVME drive I could find is 8TB which is a significant in both capacity, and cost. NVMEs are more expensive than SATA, but tends to be preferable since the memory module is so compact. You can fit 2 NVMEs in the same space as a 2.5″ SSD?. The only drive module faster than NVME is those integrated into the motherboard which every Mac computer does this method. Obviously if the storage is soldered on the motherboard, it can’t be upgraded, or replaced. NVME is a good compromise between integrated, and SATA