An sgf file extension is related to the Smart Game Format, a file format that was designed to store game records of board games for two players. Probably obsolete format.
SGF file extension - Smart Game Format
What is sgf file? How to open sgf files?
File type specification:
The sgf file extension is also used for Smart Game Format, a file format that was designed to store game records of board games for two players.
It's a text only, tree based format. Therefore games stored in this format can easily be emailed, posted or processed with text-based tools.
The main purposes of SGF are to store records of played games and to provide features for storing annotated and analyzed games (e.g. board markup, variations).
This sgf file type entry was marked as obsolete and no longer supported file format.
This type of file is no longer actively used and is most likely obsolete. This is typically the case for system files in old operating systems, file types from long discontinued software, or previous versions of certain file types (like documents, projects etc.) that were replaced in higher versions of their original programs.