A minor chord is the same as a major, but with the third flattened (the third note you'd play in the scale taken down 1 fret). Scales are more complex though.

The Church Modes (Ionian, Dorian, Phrygian, Lydian, Mixolydian, Aeolian & Locrian) are all scales built on each degree of a major scale. Play the intervals of a major scale, but start on each degreee of the scale in turn - thats how the scales are built. A Dorian and B Phrygian have the same notes, but sound different because of how the intervals are arranged. I'd say that sounds like too much to worry about right now. When people say to use 'the' minor scale, they mean natural minor which is aeolian, but one of the others might work as well / instead - you have to use your ears. Start with major and minor (Ionian & Aeolian) and build from there.

The Harmonic Minor is a natural minor (Aeolian) scale with a sharpened 7th. Harmonic Minor then has it's own modes, much like the church modes for major, but obviously it's all different scales.

Hope that helps - it's a big topic! :D