Library folder

Library is the name of several folders on a Macintosh running Mac OS X or macOS. It is typical to see several Library folders within a Mac's startup volume, which have important roles in the operating system.

Library folder in the root directory
The Library folder in the root level of the Mac OS X startup volume contains application and resource files which are used on a systemwide basis across all users.

Library folder in System folder
The Library folder in the System folder contains files for direct use by the operating system.

Library folder in home folders
Inside the home folder of every user is a Library folder which contains items available only to that user.