Pitches of music vibrate at different frequencies, with the standard tuning pitch being A 440Hz. Each pitch vibrates at a slightly different rate, creating a new note. The notes are separated out into octaves, or groups of eight closely related pitches. Each octave contains notes labeled from A to G. The ear perceives each note with the same name as having a similar sound, but higher or lower in pitch. For example, if you hit an "A" on the upper part of a piano and an "A" on the lower part of the piano, the ear will understand that they are both the same note, but as a higher and lower pitch class.
A musical staff contains five lines and four spaces. Notes are arranged on those lines and spaces to tell the player which note to play. There are two clefs that are commonly used: The bass clef and treble clef. For beginning piano, the treble clef is played by the right hand and the bass clef by the left. In piano music, the clefs are joined together and called a Grand Staff. The treble clef is used for high-pitched instruments like flute, clarinet, trumpet and violin. The bass clef is used for lower-pitched instruments like tuba, bassoon, trombone and cello. Treble clef is also sometimes called a "G-clef" and bass is called "F-clef." On treble clef, the lines represent the notes E,G,B,D, and F. The spaces are F,A,C, and E. Most people are taught to remember the line notes with mnemonics like "Every Good Boy Deserves Fudge" and remember the spaces as the word "FACE." On the bass clef, the lines represent the notes G,B,D,F and A. The spaces are A,C,E and G. Some common mnemonics for this clef are "Good Boys Do Fine Always" and "All Cows Eat Grass."
In between the lines and spaces are accidentals. These are represented by the symbols "#" for sharp and "b" for flat. Sharps raise the note by half a step, while flats lower them. It is easiest for most beginners to think of the accidentals as the black notes on a piano. If you hit a white key "G," it is a basic note. If you move up to the black key next to it, it is now a "G#" or "Ab." Now go instead to the black note below it. This is a "Gb" or an "F#."