Every pitch that you hear or note that you read in music has a name. That is what is used to identify that pitch. It's just like how you have a name that you go by and so do I. People are less likely to get us confused because our name identifies who we are and separates us from each other. The same is true for music notes.
A standardized system of seven letters was developed to help us name pitches and identify them. Now we know that "C" is different from "G" when we hear it and play it. The musical alphabet only uses seven letters: A, B, C, D, E, F, and G. Once the note "G" is played, the very next pitch is called "A" restarting the musical alphabet all over again. The entire musical alphabet can be cycled through many different times in a single piece of music.
When you look at the white keys on the piano, you will see a repeating pattern of the seven letters used in music. I tell my students that if they want to play a trick on someone, ask them to play or sing the note "H". You'll soon find out if that person really knows something about music or not.
I know it can be hard to believe that music only has seven notes, especially when you are listening to a very complex piece of music. Sometimes the pitches fly by so quickly, you have a hard time keeping up with what's going on. In whatever way music sounds to your ear, there are still no more than seven different notes that you are hearing.
Some of the notes may sound higher or lower than others. They also may be altered by a sharp or flat, giving it another very unique sound. Nonetheless, music is a simple language to learn because it only uses the first seven letters of the English language alphabet to name the notes.
Now that you know what letters are used in the musical alphabet, try memorizing all seven notes. Also, it's very worthwhile to memorize the pattern on the white keys of the piano as well. Remember to practice repeating the musical alphabet by restarting with the letter "A" after you reach "G". As you can see, music really isn't that hard to learn. The next step is to see how those seven notes are used when we read it on the music page.