This is another popular version of the major scale for guitar. The root note is based off of the 5th (A) string. The pattern is very similar to the 2nd Major Scale pattern
Scale Patterns are moveable scales where fingerings don't change from key to key. The root note (green dot) names the key of scale. What does this actually mean? It means you simply learn this pattern and you immediately know all 12 keys. You just need to place it on the correct fret to play the scale in a particular key.