Another movie that I say I hate, but it just confuses me: 2001.
If you want to understand the film, read the book. Everything you don't understand in the movie is explained. Some people have the opinion that the book explains too much & doesn't let the audience draw their own conclusions. But I think it really enhances the movie experience.
I really liked the movie before reading the book, but now I LOVE the movie.
I can also understand the frustration some might have, needing to read the book in order to understand the movie. But again, I think they did it right b/c the explanations in the book would not translate to film well & I like it left as being implied rather than implicitly stated in the movie.
If you want to know the basic premise.... SPOILERS AHEAD
It's aliens. They plant the monoliths at key points in the evolution of man. they planted the seeds of life on earth, then come back to check up on it. The aliens started as mortals like us. then as their technology advanced past nature, they transfered their consciousness into machines. Then they evolved to the point that they had no bodies at all, being essentialy gods. & now man is on the same journey & dave bowman is the first human to transcend the need for a physical body.