The following is a video produced by NASA, describing the "Seven minutes of Terror", otherwise known as the landing of the curiosity rover.
Curiosity is arguably the most complex independent robot ever built, and this landing sequence is beyond a doubt the most difficult ever. Because of the radio delay between here and Mars, the lander cannot be driven by a human operator. It must operate all by itself. If everyone did their homework, it should work. If someone came in one day with a bad hangover and slacked off, it could be years of work down the drain. Hopefully everyone triple checked each other.
I'll let NASA describe it to you. They know all about it. Please watch this video, it's well worth the time.