A ZIP file is a compressed file format that allows users to bundle multiple files and folders into a single file. This compression reduces the overall file size, making it easier to store and share. ZIP files are commonly used for sending large amounts of data over the internet or for organizing files on a computer. To access the contents of a ZIP file, users need to extract or "unzip" it using software that supports this format, such as WinZip, 7-Zip, or built-in tools in operating systems like Windows and macOS. This process restores the original files to their full size and structure.