Canon sent me this link to a very handy photography glossary.  Here is a sample entry for a term of great interest to bird photographers:

The Basics:

AI Servo AF is a selectable AF mode, for when shooting through the viewfinder in an EOS DSLR. Short for Artificial Intelligence Servo Automatic Focusing, AI Servo is Canon’s dedicated focusing mode for moving subjects.  It has the ability to track and analyse movement, and focus the image based on where it predicts the subject will be at a given point in time. AI Servo AF is the preferred focusing method for Sports photographers, and any kind of photography where the subject is constantly moving.