OK, well you haven't gotten to the lesson on inversions yet

It just means the order that the notes of the chord appear.
In a C major chord, if the bass note is C that's called root position (I think). If the bass note is E it's first inversion, if it's G it's second inversion.
Try it on the piano: play
C-E-G in that order from the bottom up. That's root position.
Then E-G-C that's first inversion
G-C-E is second inversion.
Notice that the root position sounds more "settled", like it could be the last chord of the piece. The other two sound more restless, like you're going to go to another chord next.
A lot of times in harmony, the bass line has a life of its own. Sometimes in a theory class you'll just be given the bass line to harmonize, without being told what chords to use on top of it. So a C followed by a B could be harmonized as
C-E-G
B-D-G a V chord in first inversion.
or alternatively B-E-G, a III chord in 2nd inversion. If you then change that G to a G#, you've got a perfectly acceptable progression in Romantic and later music. It would usually be followed by an A minor.