(1) Imagine your daily job is to be controlled by others, basically you move, do and say as they like.
(2) This is the general concept the director try to expose in his film. The story happened in 2034, when mind-controlling technology is taking the world by storm. Kable (Gerard Butler) is being control by Simon (Logan Lerman) in online game Slayer, designed for inmates waiting for death penalty, in a mass-scale deathmatches. Any inmate who lives through 30 matches wins his freedom.
(3) There's so many conflicts inside this movie, and I can't describe all here. However, for me Gamer was a very interesting story, about probability that some day technology will be taking over us, and at last bring destruction to our world.