All chords are derived from scales. Simple chords have three or four notes taken from basic scales (like the major or minor scale) whereas more complicated chords can have anywhere from four to seven notes played at the same time from more complex scales.

Below is a list of the intervals that some basic chords are constructed with. If you have troubles understanding this revisit the interval subsection.

Major - 1st, 3rd, 5th
Minor - 1st, b3rd, 5th
Major 7th - 1st, 3rd, 5th, 7th
Minor 7th - 1st, b3rd, 5th, b7th
7th - 1st, 3rd, 5th, b7th

Try to analyze an E major chord. There are three different notes played at the same time. The root note is an E (which is why it is called an 'E' major) the third is a G#, and the fifth is a B. The same is true for the E Major scale. The third step of the E Major scale is a G# and the fifth step of it is a B. This is why we can say that the E Major chord is made of the first, third, and fifth of the E Major scale.

Chords are constructed using every second note (you may have noticed that 1, 3, and 5 are all odd numbers) This is why logically we add the seventh interval for the next kind of chord. An E Major 7th is made of the first, third, fifth, and seventh intervals of the major scale.

You can apply the interval terms such as 'diminished' and 'augmented' in describing chords. If a chord contains the intervals 1st, b3rd, and b5th, then it is called a 'diminished' chord. If it has a 1st, 3rd, and b5th then it is called a 'diminished major' chord. The art of naming chords is definetly not a simple one. There is usually multiple ways of naming a chord. The important thing about it is that you can transfer the information in a name that people can understand.

Here is a list of some more complex chords. This will hopefully help you in naming more complex chords...

Major 9th - 1st, 3rd, 5th, 7th, 9th
Diminished - 1st, b3rd, b5th
13th - 1st, 3rd, 5th, b7th, 9th, 11th, 13th
Minor 11th - 1, b3rd, 5th, b7th, b9th, 11th

There is another aspect to naming chords. It is when to use an intervals first or second name (for example when to use a 'fourth' or when to use an 'eleventh' which are the same interval) Lets say that we are making a Major 9th chord. A 9th is the same as a 2nd, remember. This chord would contain a 1st, 3rd, 5th, 7th, and a 9th. But lets compare it to a Major Second chord. That particular chord would contain a 1st, 3rd, 5th, and 9th (or 2nd). Notice that there is no 7th. This is because when you say 'ninth' it means to use every odd number until you get to a ninth, and then stop. When you say 'second' it implys that you add on the second interval to a basic major chord.