Here's one way of looking at it. Let's say we have a class. The students in the class are named Jim, Ruth, Sally, Bob, Jim, Sally, Bob, and Ruth. It becomes confusing when the teacher calls out, "Sally, what is the answer?" Both Sallies want to answer. The same thing happens when the teacher says, "What do you think, Bob?" Both Bobs respond. So they come up with an idea. They'll use their first name followed by the first initial of their last name as a way to identify each student. So, Sally Smith will be Sally S. and Sally Williams will be Sally W. Bob Chase will be Bob C. and Bob McKoy will be Bob M. Each student assumes a new name: their first name followed by their last initial. Now, when the teacher wants a response, she asks, "What do you think, Bob M.?" This is similar to pitch and pitch register. In our system, we have more than one key on the piano which has the name of A (just like in the class we mentioned there are more than one student with the name of Bob). We have more than one key on the piano which has the name of B (just like in the class we mentioned there are more than one student with the name of Sally). All of the pitch names we use have several keys with the same name. If I ask you to play the pitch A on the piano, you would ask, "which 'A' should I play?" So, we've devised a way to identify specific keys We use the pitch name, but we add information which makes each key unique. We don't say, "please play an A." We say, "Please play a1."
We use the following system:
All of the notes in a specific register use 3 capitol letters to designate their names. The notes in that register will have the names CCC,DDD,EEE,FFF,GGG,AAA, and BBB. All of the notes in the next highest register will use 2 capitol letters. These names will be CC,DD,EE,FF,GG,AA,BB. Note that each register begins on C and continues until B and then it changes on the next C. This system continues with single capitol letters, then small letters, then small letters follwed by the number 1, etc.
See also Half and Whole Steps FAQS