What are zip file?
The ZIP file type is primarily associated with 'Compressed
Archive File'. A .ZIP file is a compressed archive.
It can contain only one file or many files in multiple
directories. ZIP utilities allow you to extract single files or a
complete directory structure. The ZIP file format is a common
archive and compression standard. This module provides tools to
create, read, write, append, and list a ZIP file. Any advanced use
of this module will require an understanding of the format, as
defined in PKZIP Application Note.
here you can find more information on this subject
http://how-to-zip-a-file.com/#about