Youtube is a video sharing platform where users can view and upload video content.
Each users’ space is arranged into “Channels” and users can arrange their uploaded videos into “Playlists”.
As well as regular users, companies like TV news channels, film studios & record labels also have accounts on the platform so that they can showcase live TV news, music videos and movie trailers.
The social element of the platform is where viewers can comment on particular videos and in some cases live message threads can run alongside long running video (such as live events of news channels).
YouTube is owned by Alphabet (they also own Google) and based in California USA.