The harp is played using the thumbs and first three fingers of each hand - harpists don't use their little fingers as they're not long enough. The fingers are played at an angle to the string and as the fingers come off they go into the palm of the hand.
Chords on the harp are very common, but composers must be careful to make sure they fit within the hand span of the harpist.
Root chords and first and second inversions are very common, but wider intervals within chords are only possible between the thumb and first finger, but not between the first and second fingers.
On the harp, the trill is very different from say, a violin.
Instead of alternating between two different notes a semitone apart, a harp trill is two strings, playing the same repeated note, over and over in quick succession. The result is that this kind of trill is much more resonant.
Bisbigliando ("whispering" in Italian) is a tremolando (rapidly repeated notes, not in time) on a whole chord. Because of the pedals on a harp, sometimes the enharmonic equivalents of notes need to be written, to make a bisbigliando chord work.
For example if you wanted an F in the same chord, you'd need to write an E# (which is the same as F) and an F as the effect is usually achieved by both hands playing adjacent strings, set to the same pitches. Bisbigliando is written as chuchotant in French and flüsternd in German and murmurando in Spanish.