Long runs involve increasing your usual running distance. If you run an average of 2km a day, you can take it up to 3 or 5km. Long runs help increase your endurance, and make you stronger as well. The longer you are able to run, the better you get. Remember to increase your distance gradually, and take occasional breaks to let your body rest.
Running on different terrains, such as roads and hills, helps your muscles to develop. Gravity plays a big role on helping you develop your muscles on elevated terrains, since you use more force to push yourself up. Remember to run on a terrain slowly at first, and let your body get used to it first. This will help you avoid accidents and injuries.
Speed workouts are good intensive workouts for you to try once in a while. In speed workouts, you focus on developing your speed, by performing plyometrics, sprinting workouts or other exercises. Your speed will improve dramatically if you incorporate speed workouts into your running for about 2-3 times a week.
Tempo running workouts basically involves running hard at a sustained pace for a period of time. This type of running workout improves your running power if you gradually increase the time you do the workout. Your muscles are able to adapt to the current tempo, and you are able to exert more force every time you run.