The first things you'll typically learn will be:
Names of the strings and why they're named what they are
How to tune the guitar
The 12 notes in the scale from root to octave (naturals, sharps and flats)
The open chords
Diatonic major and minor scales
How to form chords from scales, triads (major, minor, diminished, augmented)
Chords with additionals (7ths, 2nds, 9ths, 13ths, 6ths, etc...)
Melody and harmony
Substitution
Everything else