Tableau Prep: Tableau prep helps to combine, clean and transform for data analysis
Tableau Desktop: Tableau Desktop is a software which helps you build interactive reports, dashboards and stories
Tableau Server: Tableau Server lets you share your work done in the Tableau Desktop
Tableau Online: Functionalities of Tableau Online is similar to Tableau server, but the information is stored on the servers which are maintained by Tableau
Tableau Mobile: Users can access their dashboards/reports through Tableau Mobile app which can be downloaded from AppStore (iOS) or GooglePlay (Android).
Tableau Public: Tableau public is free to use software. Tableau Public functionality is similar to Tableau Desktop with limitations. Through Tableau Public you will not be able to save your work instead you need to publish on a cloud platform by registering on https://public.tableau.com which can be accessed by anyone.
Tableau Reader: Tableau Reader is a free to use software. Tableau Reader allows users to view reports/dashboard developed using Tableau Desktop.