What is to extract a file?

Without more specific information, this is a difficult question to answer. Extracting a file refers to the process of taking it out of a compressed format (*.zip, *.rar, *.tar, etc.) and placing it in a new folder by itself (or, more likely, as a group of files).

For example, the terminal command

tar -xvf filename.tar

would unpack/extract the file "filename.tar"

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