G
That is called the "base" of the chord. Try not to get this word confused with "root," which is the lowest note of the chord if it is in root position. Root position is when the chord is built up in thirds. Ex: C, E and G make up the C chord and the root of the chord "C" is also the base note. If this same C chord is mixed around so that G is the lowest note then higher in order is C and then E, then G would be the base note of the chord.
A bass note is the lowest note of a chord played or notated - or a note occupying a bass range.
triad
It means the root of the chord is the lowest note being played. If it's a C-major chord, the C is on the bottom.
Depends on the chord.
A second inversion chord has the fifth of the chord as the lowest note. One example is in "Ubi Caritas" as harmonized by Douglas Brooks-Davies. In measure 26, on the second syllable of "lites" there is a D minor chord built (bottom to top) as A-D-F (instead of D-F-A in root position). But any song could be arranged with a chord in the inversion. The above reference is to the vocal parts in "ubi Caritas." If you strum an A chord on guitar, the lowest note is E, the 5th of the A chord.
no
three-note chord (apex)
The III note is A. However, the 3rd note in the chord is the V note. That is C. The F major chord is F, A, C.
The letters and numbers appearing above guitar music indicate the chords to be played. The letters indicate the root of the chord (for example - G means a G major chord, but a G/B would be asking you to play a G major chord, but have B as the lowest note heard). The numbers indicate variants on a chord, such as a suspension to be resolved, or a chord with an added 7th tone (for example, G7 would be a G chord, but add in the seventh note above, an F for a bit more interest).
I think it was called an 'Arpeggio'