The Collective Bargaining Agreement is, in fundamental terms, a labor agreement between the player's union (the National Basketball Player's Association ) and the NBA itself. In fact, the NBPA has the whole sh'bang (all 43 articles and exhibits A through J-2) posted on their website for you to peruse.
In practice, suffice to say that this is the document that outlines the way that players are contracted to play for teams in the league.
This enemy of the forest covers EVERYTHING. Sure, there's the regulations most people have heard of like free agency, trades, waivers, rosters, scheduling and the All-Star Game. But there's also some lesser known, but very interesting, stuff on agent regulations, pension specifics, facility playing-conditions and broadcast rights.
The amount of detail and verbosity of this document almost make you thankful for lawyers. Luckily, Mr. Larry Coon has created the best distillation of said document known to man. And, if you're lucky, he'll answer your specific question over at RealGM.
Instead of forcing you to read through my ramblings on contract law or forcing you to go dig through the CBA or the aforementioned FAQ, I thought I'd open the floor for questions.
So lay it on us; you ask the questions, I'll dig up the answers.