The difference between a motorcycle permit and a motorcycle license is essentially what you are allowed to do with them. Though both allow the holder to drive a motorcycle, they each give the holder certain permissions. Essentially, a motorcycle permit allows a person to learn to drive a motorcycle while a license allows the holder to drive one at any time.
Though motorcycle permits may vary depending on where you live, most allow you to learn to ride/drive a motorcycle and practice safe driving skills. Typically, a permit allows you to drive a motorcycle, but prohibits you from carrying a passenger as you do so. Additionally, many states place restrictions on when you can ride your motorcycle with a permit. Usually, the holder of a permit may only drive during daylight hours. With a motorcycle license, you may carry a passenger and drive a motorcycle whenever you want, as long as you obey all traffic laws.
In many states, a driver must obtain a motorcycle permit as a prerequisite to earning a license. To do so, the driver must pass a vision test and a written or knowledge test; he or she is usually charged a nominal motorcycle permit fee to take the test. Upon passing, the driver is given a permit that is valid for a specific amount of time. Generally, the driver must practice driving and pass a road test within the period of time given. If the person fails to do so, he or she will usually be required to apply for a new motorcycle permit.
Obtaining a license is a bit different from obtaining a motorcycle permit. To obtain a license, a driver must pass a road or skills test and pay a nominal fee. This involves having a permit and demonstrating the ability to operate a motorcycle safely. For example, the driver may be required to demonstrate the correct way of using turn signals and headlights. Typically, the license seeker will also have to show that he or she can actually drive a motorcycle, demonstrating the proper execution of turns, stops, circles, and figure eights.
In some locations, drivers have an additional option for obtaining motorcycle licenses. Instead of going through the whole practice/testing process, the license seeker may enroll in an approved motorcycle safety/skills program. Upon completion of such a program, the individual is granted a motorcycle license. Generally, a motorcycle permit is required to begin this type of course. Some places offer these courses for free, though the license seeker may still have to pay for the cost of the license.