The universal term for the part that provides power (Mod) to the part that holds your juice and heating element (tank and coil), the name originates from the very first vaping power assemblies being literally Modified flashlights. These days countless companies specifically manufacture battery assemblies for vaping, nonetheless the term has stuck.
You'll generally also want something to hold your juice and vaporize it, in addition to one of these fine parts. Check out our excellent selection of Tanks. Hobbyists rocking the mech mods should peruse our exquisite RDAs and RTAs.