Since you're looking for a "deep feature" on this, it's important to clarify what you need. That term could mean a few different things in this context:
That phrase refers to a specific Russian educational resource: stands for Gotovye Domashnie Zadaniya (Finished Homework Assignments) for the 4th-grade English workbook by M.Z. Biboletova .
A breakdown of the key grammar topics (like Present Simple vs. Progressive) and vocabulary themes covered in that specific workbook.
