Tableau server acts as a middle man between the data and Tableau uses. Tableau Data Server allows you to share and upload data extracts, preserve database connections, as well as reuse calculations and field metadata.

This means any changes you can make for the calculated field, data-set, aliases, definitions or parameters, can be saved and shared with others, that allows for a secure, centrally managed and standardized dataset as well as you can leverage your server’s resources to run queries on extracts without having first to transfer them to your local machine.