Zip is the most popular data compression and archive format. A
ZIP file contains one or multiple files. Usually, the files in a zip file are stored in compressed form to take up less space in storage or take less time to send through network. A
ZIP file can also contains a password to protect sensitive files. A ZIP file usually ends up with a ".zip" extension.
The zip format was originally introduced by PKWARE in 1989. Now, it becames the most popular achive format in the world. It is also supported over almost all operating systems including Windows, Mac OS and Linux.
In order to use a ZIP file, you need unpack its contents. For encrypted ZIP file, you will also need input the correct password. The zip file is so popular that all archive utility support this format.
Sometimes, you can download self-extracting zip file from the Internet. Typically, it has a ".exe" extension, and will automatically extract and store indivisual files by double-clicking on it.
WinArchiver can do everything with zip files. It can create, modify, and extract zip files. Using WinArchiver Virtual Drive, it can even mount a zip file as virtual drive, which allow you access files in ZIP file without unpacking its contents.
Official ZIP file format: https://www.pkware.com/appnote.txt