Program files your OS needs to function. Best not to tinker with these.

Encoding data to take up less space. ZIP and RAR are common compressed formats.

Settings that control whether a user can view, edit, or execute a particular file.

A small file that just points to another file, folder, or program. Handy for quick access.

Files configured not to show up in regular file browsers. Usually system files.

The part after the dot in a filename, like .jpg or .mp3, that tells you its format.