These two different flavors of SSDs refer to their form factor as well as how they interface with your computer. M.2 SSDs are currently the most popular choice due to their superior performance and ease of installation. No larger than a stick of gum, these SSDs simply slot into a free M.2 port on your motherboard without the need for cables. However, they do tend to be more expensive.  SATA SSDs are less expensive but need to be connected to both your motherboard and power supply in order to operate. Besides needing to be tethered with cables, SATA SSDs also need to be placed in a drive cage or other mounting solution inside your case, making them slightly more difficult to install.