There are many major, minor and other types of chords in Western music, but there are only three diminished chords.
A diminished chord (at least the diminished seventh chord) is a group of three minor thirds. A minor third is an interval of three semi-tones. A nice explanation can be found on www.simplifyingtheory.com.
If we create a diminished chord on C, the following keys are selected: C, D#, F# and A. We can do the same for the next two half tones (i.e. C# and D). In this way, we create the following three chords:
[1] C D# F# A
[2] C# E G A#
[3] D F G# B
In fact, these three chords contain all the twelve notes of an octave. Therefore, all remaining diminished chords can be constructed from the inversion of one of the above three chords.
We can illustrate this by creating the diminished chords of the next two half tones (i.e. D# and E). This will create chords [4] and [5], which use the same notes of respectively chords [1] and [2] in a different order:
[4] D# F# A C
[5] E G A# C#