Running is a great way to exercise and will enable you to tone up, lose weight and improve your health and fitness. Running short sprints is anaerobic exercise (without oxygen) where as longer distances aerobic exercise.
Running will improve your cardiovascular system and will increase you fitness level and stamina. You can choose to run a session on a Treadmill and use a predefined schedule or you could run outside and formulate various routes and sessions to suite your goal.
Running outdoors can be done over cross country or multi terrain to increase endurance further, or you can do quicker flatter courses on the road to improve speed. If you are interested in improving your running then there are many running clubs that compete in local races, leagues and competitions.
Your running will also improve if you vary your sessions and have a training schedule. Your training may incorporate some resistance work (which will help your strength), interval training, circuit training and recovery or tempo runs. Runners World and other running sites will have good training schedules for various distances.
Running is liberating, you can run almost anywhere in the world and all you need is a pair of shorts and the trainers. Make sure you have good trainers with enough support to avoid injury.