I believe there are two types of motivation; External and Internal.
To me External motivation is motivation that comes from an outside source; movies, music, coaches, cheerleaders, friends, etc. This is the easiest motivation to have because it can be found anywhere.
Internal motivation is motivation that comes within yourself; your true goals and desires. Some may think that just because you "want" something, that you also are "motivated" to obtain it; which I don't believe. Anyone can "want" to lose weight, "want" to find a better job, "want" to learn a skill, but unless you find that "motivation" to obtain that "want" it will just be a "dream" or a "wish". This is the kind of motivation that really drives us to achieve our goals and is the best kind of motivation. It's the kind that will help you get through the tough times and times of doubt.
External = Someone saying "You can do it."
Inernal = You believing "I can do it."
The downside to external motivation is that it is very temporary. It usually doesn't last much past the point when the cheering, the song, or the video ends. A great example is having a coach push you in a practice or workout... chances are a person couldn't push them self when they are working out as much as if they had a coach or trainer with them.
But something great can happen with External motivation... it can lead to Internal motivation. If you help a friend or loved one see that they can achieve what they want... and the only thing stopping them is themselves. Then the realization may set in and the desire to achieve their goal will turn into Internal motivation.
Here is a great video. One that may create External motivation... and with any luck perhaps some Internal motivation.