How to compare a webcam image/video to a specific image/video?

I am basically just starting out in computer programming; mostly fluent in basic c#. I have an idea of creating an ASL (American Sign Language) to English, and my initial problem is how to identify hand movement from a webcam then comparing them to Signs that is already stored as an image or another video. If the problem is a bit too advanced for me then please list any major concepts that I can learn.
 
Please and thank you.