On the show, Gervais plays Andy Millman, a middle aged man with no family to speak of, who, upon getting close to turning forty, decides to ditch his job and follow his dream to become an actor. Where he ends up, however, is doing various extra work with his ever present friend, Maggie, who is also trying to make it as an actress. He also, occasionally, has to deal with an arch nemesis type character in Greg, a fellow extra who ends up getting more high profile work in the first series, and in the second series ends up becoming a legitimate actor.
Each episode of the show is based around someone who is "legitimate" - Kate Winslet, Sir Ian McKellan, and Daniel Radcliffe (in my personally favorite episode), for instance. For thirty minutes we see how Andy and Maggie deal with having these stars around, and, basically, how they make asses out of themselves. The second series is a little different, as, by this time, Andy has sold his spec script to the BBC and has developed his own show. The only problem with it is the fact that his piece of high entertainment, has been commodified and made into low brow trash by the BBC. Andy spends the second series trying to regain some sense of artistic integrity and legitimacy, but, often times, ends up making things worse for himself.
Extras is a hilarious cautionary tale about the realities of fame. I think the character Tre Cooper (Andy's new agent in the Series Finale) said it best when he said (something to the effect of) - "You can either be rich and famous, or you can be artistic and struggling, but you can't be both." While I don't believe that is particularly true, it is for Millman's character, because he wants the most of everything, even at the expense of a good life, and the few friends that he has.
The point of Extras, I think, is to enjoy what you have. Every time Millman tries to force things ahead in his career, it ends up blowing up in his face. Every time he tries to make himself look better, he makes himself look like a fool. It's a great life lesson, really - be yourself. You may not be famous, but its better than being false, and the people who really love you will always stay with you if you're true to yourself and true to them.
I enjoyed Extras a lot more than I enjoyed the British version of The Office. Whereas Gervais was awkward and annoying as David Brent, as Andy Millman he was somewhat endearing, even though he was horribly clueless. I liked the relationship between Andy and Maggie and how it exemplified ambition versus a certain amount of passivity. I also liked how they skewered the whole film and television world. As someone who hopes to be "legitimate" at some point in time, it made me happy that someone was pulling out some of the truths of this world, and laying them out on the table. Stephen Merchant was also hilarious as the ever bumbling agent, someone who, like so many people in the film industry, found a nitch to fit in so that they were in the industry, even though they don't actually know how to do what they are supposed to be doing.