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Originally Posted by Durero

The modes of the major scale are very old names used in the Roman Catholic Church in the middle ages. They were used in Gregorian chant and pre-date chords and 3rds based harmony.

I find it easiest to think & visualize them this way:

Ionian mode = 1 2 34 5 6 71 (= Major Scale)
Dorian mode = 2 34 5 6 71 2
Phrygian mode = 34 5 6 71 2 3
Lydian mode = 4 5 6 71 2 34
Mixolydian mode = 5 6 71 2 34 5
Aeolian mode = 6 71 2 34 5 6 (= Natural Minor Scale)
Locrian mode = 71 2 34 5 6 7

note 34 and 71 are always 1 fret apart, all the others are 2 frets apart

Excellently put! This is exactly how I think of scales and modes - by scale degree number.

Originally Posted by eleven59

When you map out all of the modes for any given key, you realize that all 12 notes are used, basically meaning that there's no such thing as a wrong note in any key.

Sorry, not correct. There are only 7, not 12, notes in any given key (and keys are based on diatonic scales). 12 notes would make it a chromatic scale. There are definitely wrong notes in any scale. That's not to say that you can't use notes that are outside of the scale and make them sound good; people do that all the time. But the whole point in learning your scales and modes is so that you can do that KNOWINGLY, not by mistake.

Since there are only 7 notes in a diatonic scale, that means there are only 7 scale shapes (excluding the scale variations, like harmonic, melodic, hungarian, neapolitan, etc), and thus, only 7 individual-string patterns (assuming you're using 3-note-per-string shapes) to remember the order of, before the pattern repeats. Trust me, it IS worth learning it.

Originally Posted by eleven59

Once I figured that out, I was ok with not bother to learn modes, which I hated being forced to memorize. I'll stick with playing whatever I think sounds good, and let the theory geeks out there tell me what I'm playing.

That also places a huge burden on any prospective bandmates you may have currently or in the future. The whole point in learning these musical systems is for the purpose of communicating musical ideas with others. The more you know (and know well) the better you can explain what you're doing so that someone else can accompany you (or vice-versa).

Originally Posted by Brett89

What is the difference between scales and modes?

Maybe I see it wrong, but are modes are same as major/minor scales?

For example: C major = C Ionian
C Dorian = A# Major

Thanks in advance!

Scales are sets of notes arranged in a particular order by interval, or how far apart they are from the adjacent notes.

Modes are when you play these scales starting on each of the notes in the scale.

For example, IONIAN is the mode commonly known as "Major", as AEOLIAN is commonly known as "Minor". So in the key of C (Ionian is always used to denote the major key, and Aeolian is always used to denote the minor key, regardless of what mode is currently being played) the modes would be as follows:

Ionian: CDEFGABC (I)
Dorian: DEFGABCD (II)
Phrygian: EFGABCDE (III)
Lydian: FGABCDEF (IV)
Mixolydian: GABCDEFG (V)
Aeolian: ABCDEFGA (VI)
Locrian: BCDEFGAB (VII)

The only difference, then, between C Major and A minor is that in A minor, you'd start on Aeolian mode. Thus, C Major is the Relative Major key to A minor, and A minor is the Relative Minor key of C Major. (Which in turn means that you could theoretically play A minor scales over a C Major chord or progression, and vice-versa.)

Aeolian: ABCDEFGA (I)
Locrian: BCDEFGAB (II)
Ionian: CDEFGABC (III)
Dorian: DEFGABCD (IV)
Phrygian: EFGABCDE (V)
Lydian: FGABCDEF (VI)
Mixolydian: GABCDEFG (VII)

============================
Building Chords and Arpeggios From Scales and Modes:

Now, with the knowledge above, you can create your own chords. Triads are 3-note chords (or arpeggios, if the notes of the chord are played individually) which are classified as major, minor, diminished, or augmented.

So, from the C Major scale, you would take notes #1, #3, & #5 -- C, E, and G, respectively -- to make your C Major chord or arpeggio. (You can also add the final C an octave above, as well, if you want; I didn't in the example below.)

C D E F G A B C

The cool thing is, you can take ANY C, ANY E, and ANY G and you will have a C Major chord. (Expanding the idea even further, you can even have a bass guitar play a C, you play an E on guitar, and have a keyboard playing a G, all at once, and it will still create a C Major chord).

The chart below illustrates which chords, and what type of chords, are made from doing this same thing at each scale degree:

C (Major): CDEFGABC
D (minor): DEFGABCD
E (minor): EFGABCDE
F (Major): FGABCDEF
G (Major): GABCDEFG
A (minor): ABCDEFGA
B (diminished): BCDEFGAB

I recommend playing through these, and as you do, pay close attention to how far apart (how many frets apart, that is) each note in each triad is from the others.

You'll see that the types of triads are constructed as follows:

Major Triad = Major 3rd (4 frets) + Minor 3rd (3 frets)
Minor Triad = Minor 3rd (3 frets) + Major 3rd (4 frets)
Diminished Triad = Minor 3rd (3 frets) + Minor 3rd (3 frets)
Augmented Triad = Major 3rd (4 frets) + Major 3rd (4 frets)

You'll notice that an Augmented Triad does not occur naturally within a Natural Major or Minor scale. It DOES, however, fall within the Harmonic Minor and Hungarian Minor scale shapes, from the Mixolydian Mode, but is not made from quite the same formula:

A Harmonic minor (Mixolydian Mode - starts on G#)
G# A B C D E F G#

A Hungarian minor (again, Mixolydian Mode - starts on G#)
G# A B C D# E F G#

Okay....that should probably overwhelm most people who are just starting out on this. Just keep referring back to it; you'll get it with time and much repetition; I did.

Good luck and enjoy!