A dripper is an atomizer, often rebuildable, that is not designed with a tank. Its interest is the simple re-filling with e-liquid: to use it, put a few drops of e-liquid on the wick(s) and you’re done. Some drippers are sometimes deep enough to stock a little bit of e-liquid.
A dripper is generally designed for expert use since the absence of a tank necessitates refilling very often and sometimes leads to dry hits. The drippers are appreciated by cloud chasers to make cloud tricks. They generally offer very aerial vaping and allow an optimal rendering of flavors.