Generally speaking, there are three (3) classifications of electric bikes.
These 3 classes of e-bikes are called:
Class 1 E-Bike
Class 2 E-Bike
Class 3 E-Bike
CLASS 1 E-BIKE
This class of electric bicycles uses a motor that provides assistance only when the e-bike is being pedaled. It stops providing assisting when a speed of 20mph is reached. Class 1 e-bikes do not have any type of hand throttle. Assistance is only achieved through actual pedaling. The motor is limited to 750 watts on all classifications.
This class of e-bike is limited to a top speed of 20mph. You can physically pedal faster than that. However, the motor will not assist you beyond 20mph.
This class of e-bike is legally allowed on all bike lanes and bike paths where traditional bikes are allowed. These include bike-only paths, parks, roads, bike lanes, and multi-use trails. They are also allowed on mountain bike trails.
CLASS 2 E-BIKE
This class of electric bicycles uses a motor that can be solely used to propel the bicycle without the need to pedal. Meaning, Class 2 e-bikes usually have a throttle that can be used to provide assistance simply by twisting or otherwise engaging that throttle. You can get to point "A" to point "B" without pedaling at all. You can throttle the whole way! The great thing about this classification is that you can do either one or both: pedal and/or use throttle! Whether you use the pedals for the boost or use the throttle, power assistance will cease to help over 20mph. As you can see, the speed limitations of power assist is the same on Class 1 and Class 2 e-bikes. 20mph is the maximum you can receive assistance on for both classifications. The only difference is that the Class 2 e-bike will come with a throttle along with the ability to just obtain help from the motor by pedaling. The motor is limited to 750 watts on all classifications.
Class 2 e-bikes will assist the rider up to 20mph whether using the pedals or throttle.
Class 2 throttle-assist e-bikes are generally allowed in most places traditional bicycles are allowed. These include all bike-only paths, parks, roads, bike lanes, and, multi-use trails. However, some local laws do not allow throttle assisted e-bikes on their traditional bike paths. You need to check your local and state laws to remain compliant.
CLASS 3 E-BIKE
This classification is the same exact as a class 1 e-bike, except for one thing: the motor will assist the rider up to 28mph. Just like the Class 1, there is no throttle on a Class 3 as well. The rider can only obtain assistance from the electric motor by pedaling. When rider exceeds 28mph, the electric motor will cut out until it detects the speed of 28mph or below. Federal regulations and some state laws indicate that Class 3 e-bikes must have a speedometer on them as well. However, most every e-bike will have a speedometer built into the display no matter what classification it falls under. Most e-bike riders want to know how fast they are traveling! The motor is limited to 750 watts on all classifications.
This classification allows the motor to assist the rider up to 28mph. No throttle is allowed on any Class 3 e-bike. The class 3 electric bike has the highest top speed of all classes.
Class 3 e-bikes are restricted from all shared or multi-use paths, bike paths, and trails shared with pedestrians. They are mostly restricted to on-road bike lanes. In some cities in Europe, a class 3 e-bike is regarded as a motor vehicle. A special license is required to ride one.