Archive file formats
15 formats in this category.
Archive formats pack many files into one and usually compress them. They are used for downloads, backups and moving folders around without losing structure.
Compression and bundling
Archive formats do two jobs, sometimes together: they bundle many files into one, and they compress to save space. ZIP does both in a single step and is the universal default, readable on every operating system without extra software. 7z (7-Zip) compresses harder and supports strong encryption, at the cost of needing a dedicated tool on some platforms. RAR is common for downloads and split archives but is a proprietary format, so most people can extract it but not create it without WinRAR.
On Linux and macOS you often meet a two-layer combination: tar bundles the files and gzip, bzip2 or xz compresses the result, giving .tar.gz, .tar.bz2 and .tar.xz. tar preserves permissions and folder structure, which plain ZIP handles less faithfully.
Picking an archive format
Use ZIP when the recipient's software is unknown; it just works. Use 7z or tar.xz when you want the smallest possible file and control both ends. Remember that already-compressed data (JPEGs, MP4s, MP3s) barely shrinks further, so an archive of media files mostly bundles rather than compresses.