Tableau has the capability to work with live data connection and also it can extract data locally (TDE).
Mentioned below are the languages used among Analyst, Tableau and Data Sources in Tableau world.
VizQL – Analyst Interactions are taken and converted into Optimized Data Source Queries.
SQL/MDX – Queries to fetch data from DB and Cubes.
TQL – Tableau Query Language to fetch data from Tableau Extract (TDE).
Result: Aggregated Results from Data Source; Tableau paints it to make easily digestible and beautiful visualizations.
QlikTab 