Why a triplane?

I am not an expert on aerodynamics so I do not know much about the
pros & cons of a monoplane vs. a biplane or triplane.
I've a re-kindled interest in the Red Baron recently and was looking
at a Fokker Triplane replica picts & videos and doing a bit of reading
about it's flying characteristics.
I have not, however, read much about the "advantage" of 3 wings. I can
guess that there would be quite a bit of maneuverability but also a
lot of drag.
Why a triplane? What are some of it's "advantages?" What are some
"disadvantages?"

Ricky