1) An authentic pick - these are picks that Edge, Bono, or Adam would actually use in concert and strum their guitars with. They are usually made by a company called Herdim that are located in West Germany. The guitar techs that U2 employ also have these picks and sometimes hand them out to fans.
2) A tour pick - these are picks that are used to commemorate the artist (in our case U2), the performer (in our case Bono, Adam, or Edge), and the tour (Elevation, 360, Vertigo). These are not used on guitars but are more like a souvenir type item that is in the shape of a plectrum / pick.
This article that was written by someone else in 2010 has the most extensive information that I've found to date and dealing with U2 picks.
U2 Picks! | Pick Collecting Quarterly
I'm going to post my collection thus far. It would be neat for other people to also post pictures of any other picks that aren't posted. I'll post ones from my collection as well as some others out there.
The front and back of a blue U2 360 tour pick. This pick also comes a translucent yellow.
The front and back of an authentic Bono pick from U2 360. Notice the Herdim micro bumps. Notice the fading of the Bono stamp. Maybe faded from guitar use.
The front and back of an authentic Edge pick from U2 360. Again, notice the Herdim bumps and the small U2 stamp.
The front and back of a Vertigo tour pick with Bono's autograph on it.
The front and back of an authentic Bono pick from the Vertigo tour.
