Particle
at; in
indicates location of action
キャシーがパーティーで何を着ていたか覚えていますか。Do you remember what Kathy had on at the party? at; when
indicates time of action
by; with
indicates means of action
Conjunction
so; therefore; (and) then; accordingly
Colloquialsee それで
by the way; incidentally; now then; well
Colloquialsee ところで