Baseball-25 and 40 man rosters

Factual Questions
1

Hey baseball fans–What’s the story with the 40 man roster? I gather that the 25 man roster contains the guys who are available to play on any given day. So who are the 15 guys who are on the 40 man but not the 25 man roster? Can they play? Do they travel with the club? What is the purpose of this larger roster?

Thanks, and go Cubs.

2

See:

http://espn.go.com/mlb/s/1999/0908/46397.html

It’s long, but the rules are complicated.