When a team releases a player, he doesn't immediately become a free agent. Instead, the player is placed on waivers, which serves as a sort of temporary holding ground as the other 29 NBA teams decide if they want to try to add him to their roster.
If a player is released between August 15th and the end of the regular season, he remains on waivers for 48 hours; otherwise he remains on waivers for a week. During that time, any team can place a waiver claim in an attempt to acquire the player. If two or more clubs place a claim, the team with the worst record takes priority. If a team claims a player off waivers, it assumes his current contract and is on the hook for the remainder of his salary. The claiming team also pays a $1,000 fee to the NBA office.
While the waiver format is simple enough, not every team has the salary cap flexibility to make a claim for any waived player it wants. There are only a few instances in which a club is able to claim a player off waivers:
The Trail Blazers' claim of J.J. Hickson earlier this season provides a perfect example of the waiver rules at work. After the Kings waived Hickson, who had a cap figure of about $2.35MM, it was widely assumed that the young forward would clear waivers and sign for the minimum salary with the Warriors, since no teams with cap space seemed interested. However, Portland unexpectedly placed a claim and was able to take on Hickson's contract using a $2.68MM traded player exception the team had gained when it traded Marcus Camby to Houston.
While the Blazers were willing to take over Hickson's contract, more often than not, waived players go unclaimed. In that case, the player's original team remains on the hook for the rest of his salary. The club has the option of using the stretch provision to "stretch" the waived player's salary and cap hit over up to twice the remaining years on his deal, plus one. For instance, if a team waived a player with one year and $6MM on his deal, it could stretch the contract over three years, reducing the annual cap hit to just $2MM.
When a player goes unclaimed, he is said to have "cleared waivers" and becomes an unrestricted free agent. If the player signs with a new team before his old contract has expired, the old team can reduce the money it owes the player, as Larry Coon explains in his CBA FAQ here. However, the original team will still be on the hook for most of the original contract.
A player waived after a certain date is ineligible for the playoffs if he signs with a new team. Typically, the cutoff date is March 1st, though it was March 23rd in this lockout-shortened season. For instance, Bill Walker was waived by the Knicks on April 20th this year, so even if he had signed with another club after clearing waivers, he wouldn't have been eligible to play in the postseason.
If a player is traded and then is waived by his new team, he cannot re-sign with his old club until one year after the trade or until the July 1st after his original contract expires, whichever is earlier. For instance, if the Mavericks were to waive Lamar Odom in the coming months, Odom wouldn't be allowed to rejoin the Lakers until December 9th -- a year after the trade.
Note: This is a Hoops Rumors Glossary entry. Our glossary posts will explain specific rules relating to trades, free agency, or other aspects of the NBA's Collective Bargaining Agreement. Larry Coon's Salary Cap FAQ was used in the creation of this post.