Before you can call any of the API endpoints, except a few that don’t require authentication, you need to authenticate with the repository so your operations are executed on behalf of a specific user. When you authenticate successfully a ticket is returned that can be used in subsequent calls to the API. A ticket is valid for a specific time, so if you don’t make any calls for a while, then you might get 401 errors back, which means you need to authenticate again to get a new ticket.