As I understand it, The NFLPA decertified as a union and is officially a "trade association." Player reps from each team approved the new CBA in principle. The next step is for a majority of players to approve reforming the union. The New England Patriots were the first team to do this, voting unanimously in favor on Tuesday (link). Once at least 50% of the players have voted for recertification there are a few issues that still need to be negotiated, but can only be done with an existing union. These include drug testing, player discipline and disability and pension programs. Both owners and players have promised that this will not be a problem and a deal will be worked out by August 4th. Then the players will vote for ratification of the new CBA.
Owners agreed to end the lockout (which players never wanted in the first place) because the players have, in essence, promised to vote in favor of the new CBA once it is finalized.
I think I'm pretty accurate here and I hope I am explaining it correctly and clearly.