Package

In macOS, a package is a directory that can contain files and / or other directories that is flagged to be presented by the Finder to the user as a single file, preventing accidental tampering of important contents. This was an important step in the transition from classic Mac OS (which relied on files containing data forks, resource forks, or both) to Mac OS X.

Folders with the following extensions are considered by the Finder to be packages:
 * .app
 * .bundle
 * .framework
 * .kext
 * .plugin

The contents can be viewed by right-clicking a package and then selecting "Show Package Contents".