A cherry picker is a type of aerial work platform

Aerial work platform

An aerial work platform, also known as an aerial device or elevating work platform, is a mechanical device used to provide temporary access for people or equipment to inaccessible areas, usually at height...

 that consists of a platform or bucket at the end of a hydraulic lifting system.
It is often mounted on the back of a large vehicle such as a truck

Truck

A truck or lorry is a motor vehicle designed to transport cargo. Trucks vary greatly in size, power, and configuration, with the smallest being mechanically similar to an automobile...

 (in which case it may also be called a bucket truck), it can also be mounted on a flat back pick up van known as a Self Drive, or sometimes on a stand-alone trailer or self-moving platform.