Don't worry. Take things easy and just go with the flow... A lot of things aren't really necessary, although they might be interesting to know. Spend time developing your style -- playing the way you want to play the songs you like.
Capo? False Nuts?
A Capo is a bar which is easily clamped over the top of the strings, to fret all the strings at a given location, forming a temporary nut. This not only changes the key of each string, but also the sequence of whole and half intervals (fret spacings) between the "new nut" and the bridge. Thus the sequence of notes you get is different. If you are in DAA and capo at the first fret, the open string are now EBB, which would seem to be E-Ionian Mode. But the sequence of fret spacings gives you the notes of Aeolian Mode, not Ionian Mode.
A False Nut is usually used by Melody-Drone or Noter & Drone players. It is a small 'stick' placed under a string (usually the bass string) to create a new nut (and new note) for just that string. The sequence of fret intervals on all other strings remains the same. A False Nut on the bass string changes the Keynote of the instrument but not the Mode (sequence of notes played on the melody string). If you are in DAA and put a False Nut on the bass string at the 1st fret you go from DAA to EAA and are still playing in Ionian Mode.