# Filter Documents and Extract Subfiles

CFS uses KeyView to extract meaningful information from the files retrieved by a connector. KeyView can extract the file content, metadata, and subfiles from over 1,000 different file types.

- File content is the main content of a file, for example the body of an e-mail message.
- Metadata is information about a file itself, for example the sender of an e-mail message or the date and time when it was received.
- Subfiles are files that are contained within the main file. For example, an e-mail message might contain embedded images or attachments that you want to index.

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