Now, i know this quite an open-ended question, but any 2 cents would help.

Am just beggining with the guitar, and am quite interested in the chord theory.

Any suggestions on where I should start reading? Books? Online articles?

I couldn't find any articles on the site explaining this theory, and things like what are pentatonics, semitones, why do some chords have major, minor and sharp (like the C-chord), while others don't?