trying to grok the NBA

My son is a big basketball fan, so I've been watching some of the NBA playoffs with him. Some things have changed since I was young, so I come to the forum with questions:
1. How can there be a 3-second lane violation on the DEFENSIVE team? Was this always a rule, or am I just ignorant?
2. The big one--just how MANY steps can one take while holding the ball before travelling is called?