If you read the first part of this book about practical theory, hopefully this will shed a lot of light on understanding the basics of chords for any musical instrument, not just guitar.
By using this book you should also be able to understand how to find and make any chord yourself.
On the guitar there are many ways to play any one chord so a bit of knowledge can go a long way.
Basically chords are related to the major scale and have a formula.
All the chord diagrams in this book show what that formula is
THE SECRET IS TO FIRST UNDERSTAND THE MAJOR SCALE and to know that
THE KEY TO MUSIC IS THE MAJOR SCALE
The practical theory module shows examples using a keyboard as this makes it easy to understand the basics of chord and scale theory.
This is written with the beginner in mind, you do not need to read music and is very easy to follow.
Once understood you should be able to understand and find both chords and scales for yourself, not just for guitar but other instruments too.