This exercise is from the Theory section on scales.

Here we play out the A major scale first, then the A minor scale so you can see / hear the difference between them. The strongest difference between these two scales is the 3rd note. In the A major scale, we play C# (also called the major 3rd). In the A natural minor scale we play C, just one fret below the C# instead. We call this the minor 3rd.

The 3rd note is really the most important note in determining whether a scale is major or minor. In this ActionTab you can probably hear that it is this 3rd note which gives the strongest differences between the two scales (although there are other differences too).

We know that the major scale intervals (root - 2 - 2 - 1 - 2 - 2 - 2 - 1 octave) will always give us the major scale for any root note.

Similarly, if you apply this series of intervals: Root - 2 - 1 - 2 - 2 - 1 - 2 - 2(octave) from any root note you will be playing the natural minor scale for that note! This is very useful for helping you learn to play any natural minor scale, even without knowing the note names!