If you are in the Olympics, you can run a mile under four minutes. The average mile will depend on age, gender and other circumstances. A mile ran in 12 minutes is higher than what most people consider to be an average time. Even for military, they require you to run two miles in 13 minutes to be acceptable and no more than 15.12 minutes.
If you are walking a mile, 12 minutes is great. However, running a mile, that is a slow time. Most athletes can run a mile in under 6 minutes. Try to improve your time by increasing your stamina and speed with some training.