Dorian
The dorian mode is found on the II degree of the Major scale. It’s one of the minor modes and its characteristic interval is the major sixth.
Scale Construction

Fingerings

Harmonization (triads)

Harmonization (seventh chords)

Harmonization (quartal)

Dorian riff
After all the theory, let’s take the guitar and play. Here’s the chart of the riff you heard in the video. The scale used is A dorian.