I could go on for ages about the team thing but I'll try to be brief. Here's a primer:
1) The advantages of drafting in cycling are such (about 30% savings behind a single rider, much more behind a pack of riders) that it is impossible for someone to "go it alone" in a stage race. (Historically they did, but that was long ago.)
2) Each team has nine riders. It's a feudal structure. The best teams have a single rider who is designated the G.C. rider. That is, he's riding for overall placement (the general classification). Lance Armstrong is such a rider. So is Jan Ullrich, etc. Depending on what the team hopes to accomplish, they might have an additional specialist or two among the nine (a climber to win mountain stages or a sprinter to win flat stages.) Generally the less hope a team has to win the whole tour, the more likely they are to have a few specialists who, on any given day, ride as though they were the team leader. (See more below.)
3) Most good times have three other kinds of riders: climbers, rollers, and domestiques. These aren't mutually exclusive categories. Their various jobs depend on the circumstances of the race, the team, the placement of the leader. It's too complicated to go into here.
4) A tour is a three week stage race. It's more gruelling than anything runners ever face. The best analogy is that each rider races a marathon every day for 21 days straight.
5) The race map has three basic kinds of stages (flat stages, mountain stages, and time trials.) The overall podium of the race is determined on the steepest climbs and in the time trials when the big guns like Lance Armstrong eventually crack the rest of the field. So to finish up, I'll give three basic scenarios to help you see how a team works together. And to make it even simpler, let's assume that Lance is not yet leading the race.
1) a mountain stage: They usually start with a gentle lead-in. It's the unspoken responsibility of the team of whoever currently holds the overall lead to try to keep the race together. Why? Well, a very motivated rider can get a big advantage in the mountains by going balls out and eating into their reserves. Even a single stage win carries a lot of prestige. So a rider who is way down in the G.C. might be allowed to ride ahead of the peloton. Up to a point. If the lead gets too big and he begins to threaten the overall lead, then the current leader's team comes to the front of the peloton and begins to hammer to bring bag the breakaway. For Lance and USPS, they'll just sit in, usually, (or maybe help out depending on tactics). Lance won't do any work. He will definitely sit in. The rollers/domestiques will bring him food/drink and block him from the wind. They'll also ride around him to protect him from other riders/crashes as much as possible. Let's say they arrive at the final couple of climbs of the day. Lance wants to crack the field. His climbers/lieutenants will come to the front of the peloton and begin to set a very hard pace. They'll ride above their limit with the knowledge that they aren't going to ride hard all the way to the top. They merely want to put the hurt on. Only the fittest G. C. riders will be able to ride in the slipstream on this pace setting while still having something left to give. Eventually, the lieutenants will be burned up, and there will be only a handful of the G. C. favorites left. They then go mano a mano.
2) flat stage--let's imagine that Lance won the mountain stage and now leads the race. He doesn't have the raw power to outsprint the sprinters. He won't aim to win a flat stage. However, he doesn't want any of his close competitors to get in front of him on the day. The best way to keep this from happening is to send your rollers up front and have them "ride tempo" on the front. The goal is to ride fast enough to discourage big breakaway attacks, except among those looking to use themselves up for one day of glory. It would be impossible for Lance to track down all the other riders. So his team does it for him.
3) time trial--the race of truth. These are individual efforts over a course, against the clock. No drafting. The only way team tactics play in an individual time trial is that Lance can ask certain riders to ride certain speeds over the course to help him get a sense of what is physically possible. Also, although not every year, there is also a team time trial where the teams ride together over a course against the clock. USPS has tended to do very well in these because they practice pacelining (efficiently taking turns leading while the others draft). A well-run TTT is a beautiful thing to watch.
Okay, that's enough. All of this is vastly oversimplified. So no digs please. It's a start. The best way to figure it out is to watch on TV. OLN will have live coverage, as well as rebroadcasts, every day of the Tour.