Chord theory is a fascinating topic. Understanding what chords are and how they are constructed on the guitar can really open your mind to a new world of possibilities.
To understand Chords, you firstly need a basic understanding of Major Scales.
Guitar Chords For Beginners
Learning chords all over the neck of the guitar is an endless pursuit and can take a life time to master. There is almost an infinite amount of voicings, combinations etc that can be constructed to produce chords.
Luckily, if you are starting out, you can get by with only a few chords. Of course the time will come when you will no doubt want to branch out and learn some more, but I would say that 90 percent of songs in the mainstream use about 10 percent of chords available, which means that you should focus on learning the main ones to start with.