A wet saw consists of a grinder body and a specialty blade mounted over a bucket. Water automatically squirts across the blade during the cutting process to keep it cool. The tile is placed on a platform that is pushed toward the blade. Then the blade cuts all the way through the tile, so the tool does all of the hard work.
Wet saws are also helpful to have when there are many tiles to cut, but once it's set up, it will be difficult to move it around. On a jobsite, that can become quite inconvenient. Cordless wet saws are a portable alternative to the standard wet saw. With a portable wet saw, the tool can be brought to the tiles, rather than bringing all the tiles back and forth to the tool.
Portable wet saws are battery powered. The small diamond blade is kept cool from water stored in a small water bottle. You can adjust the foot of the saw to make bevel cuts. Unlike the standard wet saw, which squirts water automatically while the tool is running, the water valve on the portable wet saw must be engaged manually by turning a knob.