Tributes are creations and/or stopmotions dedicated from one creator to another.
There are many types of tributes given on Creations. There are miniseries parts dedicated to a ceratin creator, a stopmotion, or even just a quick snapshot of the recipients minifigure.
There are also many reasons to give a creator a tribute. Many times, it's simply to thank the recipient for their friendship to the giver, but some are done as apologies, goodbyes, welcomes, or even contest prizes.
Tributes are generally well recepted among the Lego.com community, often used as a sign of friendship.
However, there are users who believe that tributes are unneccessary and useless.