The Wiki definition of a production company is:

"A production company, production house, production studio, or a production team is a business that provides the physical basis for works in the fields of performing arts, new media art, film, television, radio, comics, interactive arts, video games, websites, and video. Production teams consisting of technical staff to produce the media. Generally the term refers to all individuals responsible for the technical aspects of creating a particular product, regardless of where in the process their expertise is required, or how long they are involved in the project".

In simple terms, a production company will create films, videos and online content. Some companies may class themselves as a 'video production company' and only specialise in short videos. Others may specialise in social media, documentaries or corporate films.