Playing inside/outside

Can anyone tell me what it means when people say "playing inside" and "playing outside"? People say the saxophonist Charlie Parker played "inside", and that the saxophonist John Coltrane played "outside". I have a little background in music, so if it relates to theory I might be able to understand. Thanks. -Patty

"The Book of Jargon: An Essential Guide to the Inside Languages of Today" by Don Ethan Miller (MacMillan Publishing Co., New York, 1981). In the chapter on jazz, are these entries:

INSIDE: Literally, remaining within the changes (established chord sequence) of a tune. By extension, playing that is without frills or ostentation, motivated by the harmonies and melodies of the song itself.

OUT, OUTSIDE: Against the grain, avant-garde; music that is the contrary of what is expected in relation to the changes or the apparent structure employed. To "go out" means to abandon traditional jazz concepts. ("Some have gone out because they had something new to say, but most have just gone out.")