M vs : What's the Difference?

Connector Key Ngff Key Socket - 5pcs m 2 slot key m Buy Buyyart New Mini NGFF B Key SATA-Based SSD to PCI-E mSATA Adapter Card 2230 2242 226080 Motherboard only for Rs 1299 from m2_1 slot 2 SSD is a small form factor solid-state drive that internally mounted storage expansion cards use SSDs conform to a computer industry specification

m2 slot types 2 slot and my only PCIe slot is occupied by the GPU (I tried searching for an adaptor but all of them are either SATA to SATA SSD or PCIe M