Data Tables are defined based on Web Services and SQL Queries. When a data table is created, the output of the Web Service or SQL Query is represented in UI Designer as a field. This allows you to work with outputs as fields, similar to how you work with Case Fields.
You can create Data Tables in the UI Designer from the Data Panel on the left-hand menu. Data Tables use a very similar interface to Call Web Service/SQL Query action rules, except that the outputs here are bound to automatically generated fields.
Data Tables are generally created to use as lookup tables for rules, as a source for choice lists/item pickers, or to populate repeating tables. Data tables are defined based on web services or SQL queries.
As an example, a data table is created using a simple web method that returns all of the employees in an imaginary office. This method returns the same output every time.