Guitar scales
Each scale page gives the notes and formula, a full fretboard diagram with every degree marked, the chords that belong to the scale (or that it fits over), its sound and the styles that use it, plus practice tips.
If you want to start improvising, learn the minor pentatonic first — box 1 of A minor pentatonic at the 5th fret is the classic starting point — then add the blues note, and move on to the major scale and the modes.