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 for applications and the operating system. It is used to store data that could be used by multiple pieces of software, such as fonts, logs, preference files, printer drivers, sound effects, startup items, and cache files.

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 respective user. In Mac OS X 10.7 (Lion) and later, this directory is hidden by default to reduce the risk of novice users damaging or deleting its contents. It can be made visible by first opening the user's home folder, selecting  , and then clicking the checkbox for  .