Television content rating systems are systems for evaluating the content and reporting the suitability of television programmes for minors. Many countries have their own television rating system and countries' rating processes vary by local priorities. Programmes are rated by the organization that manages the system, the broadcaster, or the content producers.
A rating is usually set for each individual episode of a television series. The rating can change per episode, network, rerun, and country. As such, programme ratings are usually not meaningful unless when and where the rating is used is mentioned. From Wikipedia
