So Where comes fields in Workflow conditions. Dynamics 365 For finance and operations

During writing custom workflow. I found interesting things. Worth to share. In workflow condition screen. I did not found a lot of options. First thing I found that these Fields in conditions comes from field group we used in Approval creation wizard. But where to come child level fields. ??

Interestingly, these child level fields comes from  Workflow Document Query. Required child fields comes from child or tables in main data source of query.

Following screenshots will helps you to more understanding