Crime.net is where you choose your missions in Payday 2.

Very true. Crime.net is like a map, just with many missions that you can start or join in. There is also a Crime.net Offline. This is where you can play offline with the Payday 2 AIs which currently are not extremely helpful especially in stealth missions.

The layout is very simple. There is the name of the mission, the host, how many players are currently in game and the difficulty level of each mission. There is now an icon that shows which missions give you a bonus of stealth. The icon is a ghost.

The missions with the colour red around the boarder indicates that the mission is a pro job. This means that if you fail the mission, your contract will end. If you have just started to play Payday 2, it's recommended to avoid pro jobs. The pro of pro jobs include a much larger sum of pay and a much larger xp gain at the end of the mission.