To musicians that are heavy into learning theory scales are considered the most inmportant thing in music. You can break everything except rhythms down into scales. Melodies, chords and solos can all be broken down into scales. Scales are a series of notes that when played together give a certain feeling or style to a song. Some scales sound bluesy and some sound sad. If you were to step up to a piano and play C, D, E, F, G, A, B you would have played the Cmaj scale.
Chromatic Scale / Sharps and Flats
The first thing you should know is the notes of the guitar. There are only 12 possible notes in music. The reason there are so many keys on a keyboard and frets on a guitar is because you can play each of the 12 notes in different octaves. When you play a note an octave up it reduces the wavelength of the note by have making it higher pitched. Some notes have symbols next to them, a 'b' stands for flat and a '#' stand for sharp. Another symbol is the natural sign which looks like a box with two appendages.
The natural notes are simply A, B, C, D, E, F, and G. But there are also sharps (#) and flats(b) for some of the notes. A sharp makes a note a half step or one fret higher in pitch, a flat does he opposite and makes a note a half step or one fret lower in pitch. With these sharps and flats included the 12 possible notes are A, Bb, B, C, Db, D, Eb, E, F, F#, G and G#. This would make the A chromatic scale. Notice there isn't a Cb or Fb, make sure you can name these notes in order of the top of your head.
The top half of this chart is the chromatic scale. And the bottom half is the Cmaj scale. Notice that there is no sharp or flat between E and F and also no sharp or flat between B and C. Keep note of this. Also since each note in the chromatic scale is a half step away, if we make G flat then it will be the same tone as F#, the same goes for a Cb, which is the same tone as B.
Major Scale Pattern
Now to actually learn the major scale pattern. If we were to take the chromatic scale and take out a few of the notes we can easily construct a major scale. The major scale pattern is Step, Step, Half, Step, Step, Step, Half. Remember a Step is 2 frets and a half step is one fret. So if we were to take the chromatic scale starting on C and play only the notes in the major scale pattern we would have C, D, E, F, G, A, B, this is the C major scale.