Steel string acoustic guitar, can be played finger style, (in addition to flat pick style) using, (if you want) attached finger picks, or even 'fancy fingers' which you glue on. Finger picks is what your instructor Ernie uses or you can use just your bare fingers and even grow your nails. Jazz's Wes Montgomery used his thumb and basically made up his own style.
Even so, without a head long rush to embrace finger style, watching and flat picking along with this will be very valuable to you. Mui valuable! Tres valuable! Buy all three or start with number one and each has a useful pamphlet.
C-A-G-E-D 1 starts with the fundamentals of music theory and specifically the major scale which comprises 7 of the 12 notes of the chromatic scale and from which springs western music. Ernie entreats students to repeat the note name/number/tonality as you strum or play the scale sequentially.
The chord shape or triad is usually 1-3-5 thus learning what it means to build a basic major chord. Chords are at least three notes played at the same time in the proper sounding interval pattern. If they are then they are en-harmonic or in harmony with one another. You can hear it for yourself.
Pianos are very helpful in seeing unilaterally the major scale and represents a more visually logical configuration of notes. A keyboard will greatly augment your musical instruction manual as you can see it in a straight line.
I can't change the direction of the wind, but I can adjust my sails to always reach my destination.