This section is only an overview since this is a commonly asked question.
For training on the DataSelf (Tableau) Desktop, see the Blue Belt Training documentation.
Tableau help links:
Web Authoring and Tableau Desktop Feature Comparison - Tableau
Tableau Desktop v Tableau Web Editing
For workbook design, the Tableau Web App (Tableau Server) does about 80% of what the Tableau Desktop does.
Tableau Desktop is required to build and publish Tableau Data Sources (TDS), the data sources you see in the Tableau Web App. It is the bridge between the SQL data warehouse tables and the Tableau Site on the web.
