Modes

Sometime before 300 B.C., Greek uses different system of tones and semitones to divide the octave up and named them to people or neigbouring areas.  The Christian Church develop a method of singing called Gregorian Chant at 750 onward which uses 7 scale patterns with random Greek names.

There are 7 modes:

Ionian - WWHWWWH - major key

Dorian - WHWWWHW - mostly used in Celtic music and American folk songs originated from Irish melodies.  It gives a melancholy and soulful as the last note does not sound so resolved, like a question unanswered

Phrygian - HWWWHWW - middle east like tune.  Brighter and less melancholy than minor key.  Interval pattern is similar to Aeolian.

Lydian - WWWHWWH - with most of the intervals similar to Ionian mode except the third and forth position.  Bright as major key but with uncommon interval

Moxilydian - WWHWWHW - similarly close to Ionian mode.  Good for counterpoint to Ionian melody

Aeolian - WHWWHWW - natural minor.  If Dorian is melancholy, Aeolian mean despair.

Locrian - HWWHWWW - uncommon

The basic feel of Dorian is very close to minor which is not surprising as the different between Dorian and D minor is only 1 note (B to Bb).

Lydian and Moxilydian sound close to major key as there is only 1 note difference in semitone.  They sound slightly less definite and unambiguous.

Dorian and Phrygian sound close to minor key.  Locrian is the odd ball and not commonly used.