What does it mean? Plan stats and double rainbows.

I'm having a difficult time finding documentation on EXPLAIN PLAN stats.
For example, in
' -> Nested Loop Left Join (cost=0.43..1415.06 rows=2
width=1377) (actual time=0.093..0.093 rows=0 loops=1)'
what does 0.43..1415.06 mean? Is that a range? If so, it seems rather
pointless, like saying "somewhere between 0 and infinity".

Also, is there a way to tell the query planner to limit the search for the
best plan on a per statement basis. I know that this exists as a config
parameter but I think that applies to the entire database. I have a query
that takes 9 times more time to plan than it does to execute.

Tia,
Mike