This image highlights the notes on a fretboard that can be used to cover a C scale, with the root at the 8th fret, from three different fingering positions. Below, these positions will be broken down. These are all movable scale positions. For example if you moved to a root at the 5th fret you will be playing in the Key of A, and 7th fret in the Key of B, etc. The notes will change but the intervals will not change. Notice the Whole-Step Rule. To ascend in pitch across the strings in whole steps (two half steps), move (toward the tuning machines) three frets from where you are to the next string up in pitch (a total of four frets). The one exception to this is between the third and second strings, where the distance is only two frets away (a total of three frets). The rule can be reversed to descend in pitch. (Melbay's Guitar Workbook).
This image highlights a scale that begins at the 8th fret on the 6th string as played by using your index finger for the first (root) note, first position. It requires a stretch over 5 frets long as seen on the 6th, 5th, 2nd, and 1st strings, which is played with the little finger, so as to keep your first finger in position.
This image highlights the C scale from the second position, using the middle finger on the root note of C on the 8th fret.
Finally, this image highlights a third position, using the ring finger on the root note of C on the 8th fret. This too requires a stretch over five frets on the 3rd and 4th strings.
Here we are back again to all of the notes covered by three positions of the C scale. However in this image I have tried to highlight where notes overlap with each other, which can be useful if you wanted to change positions mid scale, but remain in the same key.
Barre Chords are movable up and down the fretboard. There are different fingerings for Barre chords, depending on what string the root is on. The root is the name of the chord. You can find different Barre chord fingerings on the Chord Generator.