Difference between tableau extensions .twb and .twbx

Twbx:

1. .twbx file is a Tableau Packaged Workbook, meaning it is the original .twb file grouped together with the datasource(s) in one package. 
2.  .twbx files can be considered analogous to specialized zip files, in which these “zip” files contain all the information necessary to work in Tableau.   
3. The primary advantage to using .twbx files is that analysis can be performed without network/internet connections to your data because your data is already present on your computer in this packaged file.

Twb:

1. The .twb file alone is not enough to perform any analysis because it only contains Tableau’s instructions for interacting with a datasource.  
2. In actuality, .twb files are XML files specially tailored to interact with datasources.
3. They are custom built to make the awesome visualizations that Tableau generates.  Here you can see a picture of a .twb file opened in Notepad++.