The DataSelf Desktop app is a modified version of the retail Tableau Desktop app designed to work exclusively with the DataSelf system.
DataSelf Desktop is installed locally on your computer, (it is not a web app), and must be registered/licensed on your computer in order to use. It is a named user license, not generic.
Link to download & install reference:
Download, Install Tableau Desktop and Server - DataSelf - Confluence (atlassian.net)
Links to Tableau help article on differences between Tableau Desktop and Web Authoring:
Web Authoring and Tableau Desktop Feature Comparison - Tableau
Tableau Desktop v Tableau Web Editing
*.twb and *.tds Files
Tableau WorkBooks (*.twb)
Tableau Packaged Workbook (*.twbx)
Tableau Data Source (*.tds)