.tds file vs .tdsx vs .twb vs .twbx

.tds file

.tds is a file extension of the Tableau data source files.
Data source files are the shortcuts for connecting to the data source quickly.
Data source files do not contain the actual data.
It contains only the information needed by the user to connect to the data source such as:-

Connection information is given on the data source page example-location of local files, tables, database address.

This format is used when everyone who all are using the database have the access to the underlying file defined in the connection information.
While saving the data source the file type (extension) is selected.
By default, Tableau saves .tds files to the data source folder in Tableau repository.

.tdsx is a file extension of the Tableau packaged data source files.
A packaged data source is a zip file that contains data source files and also any local file data source such as Extract files, Excel files etc.
This format is used for the creation of single file that the user can share with the others who does not have access to the underlying data defined in the connection information.
While saving the data source the file type (extension) is selected.
By default Tableau saves .tds files to the data source folder in Tableau repository.
.tdsx files are preferred to avoid saving a specific file path.

.twb file extension is used for the Tableau workbook file.
Workbooks can have one or more worksheets, dashboards and stories.
.twb is the most common file extension used by the user.
.twb file represents an XML format file and contains all the information present in the workbook such as sheets, dashboard, styles, formatting applied.
It does not contain any data.
The .twb file is itself not enough for performing any analysis because it only contains Tableau instructions for interacting with the data source.

.twbx is a file extension used for Tableau packaged workbooks.
A packaged workbook is a single zip file that contains a workbook with background images and also any supporting local file data sources.
The files which are included in packaged workbooks are:-

This file extension is preferred over .twb as it contains the workbook along with the data source.
It is the best format used for sharing the work with the ones who do not have the access to the data source.
The advantage of using .twbx file is that analysis can be performed without internet connections to the data as the data is already present on the computer in the packaged file.
The workbook’s extension can be chosen while saving the workbook. The default location is the workbooks folder in the tableau repository. Also, the user can save the workbooks to any directory of his/her choice.
If the workbook contains connections non file based data source such as MySQL, Oracle, then firstly data must be extracted from the data source for it to be included in a packaged workbook.
.twbx file can be unpackaged and changed into .twb file by renaming the file extension.