There are five tools in Tableau, such as:

Tableau Desktop: Tableau Desktop establish connectivity between the Data Warehouse and other various types of files. The dashboards and the workbooks created here can be either shared locally or publicly. It allows us to code and customizes reports. Right from establishing the stories, charts to blending them all to form a dashboard, all the necessary work is created in Tableau Desktop.
Tableau Public: This Tableau version is specially built for cost-effective users. The word ‘Public’ means that the created workbooks cannot be saved locally. They should be kept on the Tableau’s public cloud, which can be accessed and viewed by anyone.
Tableau Online: Its functionality is similar to the Tableau server, but data is stored on the server that hosted on the cloud, which is maintained by the Tableau group. There is no storage limit on the data which is published in the Tableau Online. Tableau Online creates a direct link over 40 data sources who are hosted in the cloud such as the Hive, MySQL, Spark SQL, Amazon Aurora, and many more.
Tableau Server: The software is correctly used to share the workbooks, visualizations, which is created in the Tableau Desktop application over the organization. To share dashboards in the Tableau Server, you should first publish your workbook in the Tableau Desktop. Once the workbook has been uploaded to the server, it will be accessible only to the authorized users.
Tableau Reader: Tableau Reader is a free tool which allows us to view the visualizations and workbooks, which is created using Tableau Desktop or Tableau Public. The data can be filtered, but modifications and editing are restricted. There is no security in Tableau Reader as anyone can view workbook using Tableau Reader.