Most bicycles have external gears with the gears visible to the eye and the chain has to jump from one sprocket to the next to offer a different resistance.
With Shimano 3-Speed Nexus, the gears are enclosed inside the rear wheel. This protects the mechanism from sand, salt, and debris. Since there is only one sprocket, the rider does not have to be pedaling to shift gears. That means you can ride up to a stop sign or stop light and crank the gears from 3 down to 1 at a stand-still without pedaling.
Shimano 3-Speed Nexus hubs are extremely low maintenance. People can often go years without getting them adjusted. If you are tired of traditional gears, give the 3-Speed Nexus a try!