Question: I am learning to play guitar by myself, and it is hard to understand some theory about how guitar chords are built. For example let's look at a G chord. I have found two of the most simple definitions:

[![G chord](https://i.stack.imgur.com/zP4WA.png)](https://i.stack.imgur.com/zP4WA.png)

If we write down corresponding notes for both of them we will get:

* **G B D G** for the former
* **G B G** for the latter

But as I understand major chords are built from 1st, 3rd and 5th notes of the major scale, which is:

**G A B C D E F# C**

Therefore it should be **G B D**. Where am I wrong?

The same question is about E chord.

[![E chord](https://i.stack.imgur.com/FyV4T.gif)](https://i.stack.imgur.com/FyV4T.gif)

Notes are: **E B G** whereas according to the scale **E F# G# A B C# D# E** it should be **E G# B**.

And one more question. How is it possible for chord to have more than 3 notes, like the G chord on the 3rd fret, if the chord is a triad?

Answer: 
It's a strange concept for beginners to grasp, but yes, you're correct, a triad chord has three notes. However (there's usually one of those), there's nothing to say *how many* of each there are. One of each is fine - without all three, it's not a triad - but we then get into *voicing*, which makes each chord sound subtly different. 

Guitar is really a special case, because of the 6 strings. What I do with students at some point is to present a triad. Let's say C major, CEG. Take each string in turn, and find a C, E or G playable on it. Obviously when the notes have been found, they must be playable simultaneously, otherwise it can't be a 6 string guitar chord.

6th string could be E or G. 5th is C. 4th makes E. 3rd, open is G. 2nd finds another C, and top can be E or G. So now we have 4 different versions of Cmaj. All with *some* Cs, *some* Es and *some* Gs. All can be classed as correct, but some sound better in certain songs than others.
While there is the triad, there is all the other notes in the scale that you can add to change how chord sounds. Such as a dominant 7 on top of the triad to make the chord sound bluesy. Or a maj7 which makes the chord sound jazzy. Those are just the start to add on notes but is another way a chord could have more than just the basic triad. Learning more about the add ons and experimenting with them in progressions and such can really spice up your playing. Also it actually helps a lot with soloing on chords.