I get this question a lot, so I decided to type “default” into Spotlight … Hey, that’s cool: Spotlight in Leopard is not only faster, it also finds definitions in the built-in Dictionary, which itself now has a Wikipedia search. Awesome!
default |diˈfôlt|noun.2. a preselected option adopted by a computer program or other mechanism when no alternative is specified by the user or programmer :e.g. “the default is fifty lines” | [as adj. ] default settings.
So, a program’s defaults are the way it will behave unless you choose otherwise.