SSDs come in many varieties, capacities, and brand names. However, there is a natural technological divide that separates two classes of SSDs. Those drives that are designed for older interfaces, mSATA III, SATA III, and traditional SSDs, and those designed for high bandwidth applications, PCIe and NVMe SSDs.
PCIe — PCI Express (PCIe) is a low latency, high data transfer bus for connecting peripherals like graphics cards. A PCIe SSD will look like a PCIe card.
NVMe SSDs — Nonvolatile Memory Express standard (NVMe) offers higher input output per second (IOPS). NVMe uses multiple parallel channels to reach levels of 16 Gbits/s of throughput. Far superior to any other.
mSATA III, SATA III, and traditional SSDs — Serial Advanced Technology Attachment (SATA) is a storage interface common to HDDs. SATA is slowly being phased out and replaced by NVMe.