“The musical alphabet” consists of seven notes that are named by the letters A, B, C. D, E, F and G. The distance between each note is called an interval and varies from a whole step which is 2 frets and a half step which is one fret. Below is a picture which illustrates the musical alphabet.
Observe the reddish ties or loops in the above image. These are to designate where the half steps occur. In other words, “E to F” is a half-step and “B to C” is a half-step. Also notice that the notes keep repeating themselves; this is because even though there may be only 7 notes in the musical alphabet, there are several octaves detectable to the human ear that contain the same 7 notes. Therefore, a piano has 88 keys and not seven. One more thing regarding the musical alphabet, if you count the seven letter names along with the notes that occur between the “reddish loops” you will have a total of 12 notes making up a full octave of music.
The notes on the guitar fretboard are arranged according to the musical alphabet. You should memorize the name of each guitar string which will give you a starting point for finding all the notes on the guitar. Look down at the strings while holding the guitar in a playing position. The fattest string is called the E or 6th string. The thinnest string is called the E or 1st string with the A, D, G, and B strings between them. As the name of the 4th string open is D, when you place a capo on the 1st fret it becomes a D sharp which is 1 fret higher than D. Below is a diagram which shows all the notes on the guitar.