All salary cap rules are going to come from the CBA, but here is a list of the major rules/guidelines regarding the salary cap.
The salary cap is set at $50.3 million.
Players Salaries are determined by their salaries in REAL life. When a players salary changes in real life, it changes in this league. So have cap space, just incase some of the players get raises during the season.
In the offseason you are allowed to spend 10% over the cap but all teams must be under the cap by October 1st.
If a players salary changes and forces the team to go over the cap DURING the season, they will have 2 days from the time the contract is announced to get back under the cap. If a team fails to get under the cap they will be subject to penalty.