The film takes as its theme the idea that human evolution has been guided by aliens, and that with the advent of manned space travel we have developed the maturity as a race to directly encounter this guiding entity for the first time.
The opening scene takes place in Africa at the dawn of mankind, where groups of ape-like creatures fight for food and survival. A large, black, rectangular monolith appears, and stimulates the intellectual abilities of some of the apes, who are then inspired to use bones as tools. The transition of some apes into tool-users marked the beginning of the development of man, and set the stage for what was to come.
The story transitions to 2001, where explorers on the moon had investigated a strange radio source, and uncover a similar monolith that had apparently been buried there for millions of years. After being unearthed, this monolith emits new radio beacon aimed at Jupiter, so an expedition is mounted to investigate the target of the transmission.
The remainder of the film deals with the voyage of the ship Discovery to Jupiter. During the trip, the two astronauts actively manning the ship begin to suspect that their artificial intelligence support computer, named HAL, is malfunctioning. HAL begins to exhibit paranoid behavior as its actions are questions, and attacks the crew in apparent self-defense. HAL is disabled, and the sole surviving astronaut arrives at Jupiter to find a significantly larger monolith in orbit around the planet. He takes a shuttle-pod and lands on the surface of the monolith, at which point he undergoes a strange, hallucinatory transformation and is reborn as a god-like, embryonic entity referred to as the "Star Child".
The film is considered a classic of the science fiction genre for several reasons. Most notably, it was the most realistic depiction of space travel in cinema to that date. Meticulous detail was put into the design and filming of the spacecraft, whose actions were realistic (no sounds in space, and their movements followed the laws of physics). Interior spaceflight sequences were captured imaginatively, particularly the zero-G environments on the various ships.
The film is also regarded as being art-like, with its use of classical music in the soundtrack to set mood, and the lack of a specific narrative allowing each viewer to interpret the story in their own way.