i just watched this video

http://www.youtube.com/watch?v=U95Hvipxtig

but i dunno what minors and majors are and what i do is simple like having c5 + c6 + c7 .

so only layered noted at the same note with just 1 higher.

but how to learn chords as a newbie? what they are and how to set them correctly?

Mel Bay books.

Seriously. If you are not familiar with it, check it on Wikipedia.

Not a substitute, but a supplement

http://www.youtube.com/watch?feature=player_embedded&v=P_1Bg tA_lvo

Here are all the chords and scales showing how to play on a keyboard:

http://www.apassion4jazz.net/keys.html

Thanks, that's very helpful!

Check out my Introduction to Music Theory.

My post on Scales, Modes and Chords might also be useful.

An easy way to learn chords for the piano is to know first where all the notes are. I mean really know where the notes are. For example point to and name note within 100ms of pointing try to get down to 50ms then 25ms. Once you know the notes and names and can automatically name them in your head as you play.

Then move on to a chord chart memorize the chords in the same way as single notes. Work on chords in the same key until you can identify very quickly each variation.

Also have patience this probably will take a few month unless you can memorize and retain very quickly.

Build up muscle memory associated with note and chords and it will be like riding a bike you will never really forget.

One last thing is pay attention to the finger numbers on the chord chart match these with the note for an easier time.

i think i can already see where which note is cause of the piano roll of fl studio !

I recommend this book - Piano Chords & Chord Progressions: The Secret Back Door To Exciting Piano Playing! - Check it out on Amazon

I already know how to play all major & minor chords! Really fun and easy, take the 3rd of the major chord and bring it down a semitone and you have a minor!

Check out Cthulhu, you can record/import chords into it and it tells you the chord, has lot's of classical progressions which are fun to play with but it's educational as well. There's also Tonespace which is free.

How do you know what chords can be played in a certain scale?

I own a few books of scales which illustrate what the chords are (what a D minor/major chord is, what a sus4 chord is etc) but none give the answer to this. Say, for example, that I'm composing in C Major, do I only use major chords based upon the notes in the scale (and their extensions) or can I use minor chords etc? How does it work?

There are twelve notes in a scale. For example from C to C. For each step there is an associated chord. Starting with C the first chord is a major, then D- minor, E- minor, F - major, G- major, A- minor, B - diminished, ending with C- major. This is the same pattern for all keys. However, that does not mean that you play a different chord for each note of the scale.

Check out my Introduction to Music Theory.

To put it simply, you build chords using the notes of the key. So, in C major you have C,D,E,F,G,A and B to play with; no sharps of flats.

Chords are usually constructed in thirds; that means there is a third between each note. (C to D is a second, C to E is a third for example).

So, stacking thirds in this way on each note of the scale gives you:
C,E,G
D,F,A
E,G,B
F,A,C
G,B,D
A,C,E
B,D,F

In any major key; chords I, IV and V are major chords. Chords ii, iii and vi are minor, and chord vii is diminished.

If I was in G major for example, I have an F#, so that means I use D,F#,A and B,D,F# (instead of D,F,A and B,D,F)
If I was in F major, I have a Bb so I use G,Bb,D and Bb,D,F.
And so on.