The e-bow is a way of "bowing" the guitar strings via a magnetic field.
The device itself is made to fit the palm of your hand, and operates on a single 9 volt battery. You "hover' the e-bow over the selected string and it begins to vibrate, creating sound w/o the usual pick attack. With practice you can mimic the sound of an oboe, flute, violin, cello, etc.
It's an interesting effect, somewhat like a volume swell + sustainer effect. I'm still practicing with mine, and I'm sure there are more ways to use it, I'm a beginner.

At $99 U.S. currency, I'm sure it's not for everyone, but if you're looking for something different you should check one out. I would caution that they are made of plastic and probably wouldn't survive being dropped on a hard surface, but I believe the plastic case is a necessity as metal would not allow for the magnetic field that drives the string.

It does take some practice to position the e-bow over the string properly in order to drive the string so that it begins to vibrate. I'm just starting to get the knack of it, but so far I'm enjoying it. A trick I've learned is use a humbucker equipped guitar on the neck pickup with the guitar volume turned down a bit and the tone control down almost fully. This seems to yield the best sound to me.......YMMV.
The video below will give an idea of the sound of the e-bow used on electric guitar.