TDE is a Tableau desktop file that contains a .tde extension. It refers to the file that contains data extracted from external sources like MS Excel, MS Access or CSV file.
There are two aspects of TDE design that make them ideal for supporting analytics and data discovery.
Firstly, TDE is a columnar store
The second is how they are structured which impacts how they are loaded into memory and used by Tableau. This is an important aspect of how TDEs are ―architecture aware‖. Architecture-awareness means that TDEs use all parts of your computer memory, from RAM to hard disk, and put each part to work what best fits its characteristics.