Pro video and cinematography is exclusively manual focus. Usually, a dedicated person, called a focus puller does the actual focusing, but some camera operators prefer to pull their own focus. Focus control is done with a device called a follow focus. Changing focus is called a focus pull. Rack focus is another term, although its mostly used to describe large focus pulls, for example from one actor to another. A follow focus is not strictly necessary as you can manually turn the focus ring. However, having one on your camera allows the operator or focus puller to be more efficient and precise.