There are three types or classes of electric bikes.
Class 1
The pedal assist or pedelec (short for pedal electric cycle) is the most common. As the rider pedals, assistance is given by a small motor powered by a battery.
The amount of assistance is controlled by settings on the handlebars. The top speed cannot exceed 25km per hour (15.5 mph) within the UK. In the USA the top speed for this class is 32km per hour (20mph)
The motor output cannot exceed more than 250 watts within the UK and not more than 500 watts within the USA.
In the UK riders can start using e bikes at the age of 14 whereas in America they can start as young as 12 .
In neither country is it obligatory to wear cycle helmets
Class 2
The throttle eBike. As the name suggests a throttle similar to that found on a moped moves the eBike forward without any pedalling from the rider. The throttle which is situated on the handlebar uses either a twist and go action or a button or paddle operated by your thumb.
Throttle eBikes are more common in the USA and very rarely found in the UK because the law states that eBikes must have the pedals moving while getting power from the battery.