Use a tool like 7-Zip (Windows) , The Unarchiver (Mac) , or command-line tools ( 7z x T013.7z ) to open the file.
did you download this file? (A website, a specific forum, an email?) T013.7z
What do you expect to find inside? (e.g., "It's a game mod," "It's a datasets," "It's a software installer") I can provide more specific instructions on how to use it. Use a tool like 7-Zip (Windows) , The
