The filename suggests it is part of a numbered series (e.g., "04") within a larger collection of data.
If you received "04 Knowledge.rar" from the internet or an unknown source, follow these precautions before opening it: Need to open, create, or convert a RAR file? - WinZip
: The official software for creating and opening these files.
: The .rar extension stands for Roshal Archive . It is a proprietary format used to bundle multiple files into a single, smaller package to save storage space and make sharing easier.
Because Windows and macOS do not always support .rar files natively, you will need a third-party "unarchiver" or "extractor":
: A common choice for Mac users to extract compressed files. Safety and Security Tips
: Based on the name "Knowledge," it most likely contains documents, PDFs, videos, or course materials related to a specific subject, training module, or database. How to Access the Contents
: A popular, free, open-source alternative that handles many archive formats.