Drippers are fantastic for testing out juice flavors without having to fill a tank. I think everyone should have at least one on hand, especially while searching for that elusive all-day vape. I also use mine when my tastebuds start becoming numb to what I've been vaping and I need to change up the flavor.
If you want to know how they work, think about taking a cartomizer that has a horizontal coil on the bottom and pulling out all of the absorbent material in it; it's just an atomizer that you drip liquid directly on in order to vape it. The biggest downside is that you can't just fill it up with liquid and vape for hours on end; after every few inhales you will need to drip more liquid onto the coil. The upside, however, is that the flavor a dripping atomizer produces is fantastic.
Everyone has their favorite dripping atty's, so you'll probably get a lot of recommendations here. As far as 510 dripping atty's go, the
HH.357 Cisco Spec Hybrid 510 Atomizer - Avid Vaper is a great one. It is on the pricey side, and dripping atty's don't last forever, so you'll need to replace it periodically. The atty I'm using is the 1.5 ohm long barrel
Stingray 510 Atomizer; it works great and is about half the price of the HH.357.
There are many others out there, but I've been using 510 atty's so that's what I'm familiar with. When you decide what you want pick up a couple and try them out. There is a slight learning curve with them; it takes a little time to become familiar with the atty and know when it needs to be topped off to prevent a dry burn, but you'll figure it out pretty quickly. Good luck.