correction there are 4 types
SATA HDD (slowest but cheapest and can come in huge storage size)
SATA SSD (noticeably faster than the fastest HDD, more expensive
M.2 SATA SSD (is no faster than a normal SATA SSD, be careful as some try to trick you into buying this type by not making it clear its only a SATA drive)
M.2 PCI SSD (this is the fastest type available today, much faster than any SATA SSD, comes in a very small form factor, expensive)