At the physical end, parkour focuses on efficient movement (for example the movements you would use in a in a chase sitatuation) through any environment regardless of obstacles.
Physical prowess, dynamism, endurance, critical thinking and risk assesment are trained to allow practitioners to overcome any obstacle.

Parkour is completely non-competetive as it's practioners are encouraged to find their own way of moving. While there are more commonplace and conventional techniques - there is no strict list of movements - the only real 'guideline' is that movements focus on directness and efficiency. Movements outside of this realm such as rotations and flips can still be beneficial to your fitness and so are useful in training, but not as useful in practice.
It is important to remember that if a traceur restricts the realm of movement or places explicit 'rules' on it, they may be limiting what they can learn. The attitude and approach to learning a technique is what is important, not as much the technique itself.

Mentally, parkour teaches discipline, critical thinking, risk assessment and personal development. This is expressed and learned through the practice of movement but these skills can be applied to any aspect of life. This makes Parkour and the 'Parkour Spirit' beneficial to a traceur's life as a whole and is something that can be practiced regardless of what happens to one's physicality.

Artistically, practitioners can be seen as expressing themselves through movement, in a way similar to dance or physical theatre.
Each traceur’s movement is different, and is an example of their individual physicality, personality and spirit.