The things that I have learned so far during my guitar lessons are chord switching, picking and the basic chords which are the G major, D major, C major, and the E minor. This may seem like only a bit of chords but really many songs including praise and worship songs can be played with these few chords. As I have mentioned before learning these chords can be a struggle in the beginning and painful as well but once you've got the hang of it, it becomes very simple and and pain simmers down because of the process of calluses building on the tip of your fingers and pain is also something you get use too as you are practicing.
Recently I have been starting to practice bar chords on the guitar. From what my guitar mentor has told me, bar chords are one of the most difficult and frustrating things to learn on guitar. Most guitar players (even professionals) hated these chords while learning and getting into bar chords I can understand their struggle. What a bar chord specifically is, is a type of guitar chord which one or more fingers are used to press down against the strings across the finger board which enables the guitarist to play a chord not restricted by the tones of the open strings on the guitar.
As I mentioned previously I am also currently learning how to pick on the guitar strings. What picking is, is it's a type if technique used to allow string and sound to be in action on the right side of the guitar. The other type of technique there is is known as strumming. As me and my mentor were experimenting with both picking and strumming it was clear that I would find picking more easier to learn and have less trouble with, so I started off picking before strumming. Personally for me picking is pretty simple. The only thing that I struggle with in picking so far is just learning to pick and switch chords at the same time.