1. Tableau Desktop:
Tableau Desktop is data visualization software that lets you see and understand data in minutes. With other Tableau products, it comprises a complete business intelligence software solution.
2. Tableau Server:
It is more of a enterprise level Tableau software. You can publish dashboards with Tableau Desktop and share them throughout the organization with web-based Tableau server. It leverages fast databases through live connections.
3. Tableau Online:
It is a private version of tableau public which eliminates the need for the infrastructure.
4. Tableau Reader:
A free desktop application that allows you to open and view visualizations/workbooks built in Tableau Desktop. You can filter, drill down data but you cannot edit or perform any kind of interactions in it.
5. Tableau Public:
This is a free Tableau software which you can use to make visualizations with but you need to save your workbook or worksheets in the Tableau Server which can be viewed by anyone.
Further, enroll for an online training course to clear the Tableau Desktop Specialist Certification exam. I would recommend this Tableau Course online by Intellipaat.