hi everybody,please share your knowledge about data extraction and what is use?

As the command name implied, it's to extract data from your drawing. You can extract the block counts, the block insertion point, line length, basically almost every data in your drawing. You can try it by following this tutorial: https://www.cad-notes.com/create-a-report-table-with-data-extraction/

About data extraction in AutoCAD.  Copy and paste in your search bar.https://knowledge.autodesk.com/support/autocad/learn-explore/caas/CloudHelp/cloudhelp/2021/ENU/AutoCAD-Core/files/GUID-B0D32260-45E3-4643-B574-7F6C31579B68-htm.html