Windows and Macs open ZIPs on their own, but most other archives need extra software. Pick the extension you've got to see where it comes from, whether your computer can already open it, and the quickest way in.
An archive can carry more than files. It can hold paths that climb out of the folder you extract into (the “Zip Slip” attack), links to elsewhere on your disk, programs disguised as photos, and entries that expand a thousandfold. Drop one in and your browser reads its directory without extracting anything to disk: the ZIP central directory, or the TAR headers after un-gzipping in memory. Everything happens on your device. The first sample was built in your browser to trip every check.
Unix tools split the job in two. TAR glues files into one stream without compressing; GZIP, BZIP2 or XZ then compresses that stream. ZIP and 7Z do both at once and compress each file separately.
Your browser generates a set of files and packs them twice with the same deflate compressor: once as a ZIP, compressing each file on its own, and once as a TAR.GZ, one compressed stream. It then times how long it takes to get the last file back out of each. Every number is measured, and both archives can be downloaded and opened.
Both use deflate at your browser's default level, so the gap comes only from the layout. 7Z and RAR in solid mode behave like TAR.GZ, with stronger compressors. Timings are the fastest of three runs and depend on your device.
Everything for archives, with a typical result for each.
The fields that decide whether a format can hold your files: how big, how many, which names and dates survive, and what is protected. GZIP, XZ and Zstandard compress a single stream, which is why they're paired with TAR.
The toolboxes for whatever you unpacked.