There are two types of datasources or tables within Bright Analytics.
Data tables - this is where your performance data lies i.e. where your metrics/numbers will sit e.g. Impressions, Clicks, Cost etc. All of your metrics will be built from a column from a data table.
Meta tables - this is where your dimension values lie e.g. id, names, categories etc. This is where you can label various aspects of your data in custom columns and is usually used in a lookup capacity.
For more information on lookup dimension mappings please read the following article.
Data tables in Report Engine
All data tables must have a date field selected in the report engine datasource page. This is because the reports in Bright Analytics cannot query your data if there is no time period selected/available for your datasource.
If this field is empty the datasource will not appear as an option to select when doing dimension mappings.
Meta tables in Report Engine
To specify whether a table is a 'meta' table you must enter 'lookup' in the special type field.
Once you have saved changes (commit changes) this table will become available as an option when making lookup dimension mappings: