I have started a YouTube series to explain various concepts of OAuth 2.0. The title is "OAuth in 2 minutes". Each video is about 1 minutes long and explains various concepts of OAuth in a way that even non-technical people can understand.
The first part covers the basic concept, which anyone who has used the subway or train will understand immediately.
The audio is in English, but Japanese subtitles are available, so please turn on the subtitles when watching.