Tableau Online is simply a secure cloud-based internet platform that allows you to share views, dashboards and data sources without the involvement of local servers and IT support. In this case, the infrastructure provided by Tableau is used.
Tableau Online allows you to publish dashboards, filter and edit reports directly on the website. In addition, the user can save changes online, receive subscriptions related to reports and set up automatic data refresh. Only authenticated users have access to published data and visuals. As with Tableau Server , permissions management is very detailed.