The relationship between C major and C minor is parallel. That means that both scales share the same root. C minor is the parallel minor of C major. Comparing a C major and C minor scale is a great way to see what is the same, and what is different between the 2 scales.
All theory boils down to how notes relate to a major scale.
The major scale is the constant that is used to compare everything else. Each note in a major scale gets a number. What that means is that those notes are the equivalent of 1 fret lower on the guitar than the notes in the major scale. So there are 4 notes that are the same, and 3 notes that are different.