Inception is totally simple.
There is tech to go within dreams.
While being sedated you have the ability to make a dream within a dream.
And multiple dreams within a dream so that they are layered.
In order to see if something is a dream or not, you must create a totem. Something to tell you whether you're dream or in reality.
Inception is a movie about an attempt to heist information and convince someone of a single idea through such dream technology. It is Heat with dreams.
Like always, a totally straight forward film is labeled as "confusing" by the masses (Donnie Darko, Pi, Pulp Fiction;etc).
Note: this is coming from someone diagnosed with ADD which he really really doubts he actually has.
