/lib

A directory that contains essential shared libraries that programs need in order to run (filename .so), as well as static libraries used during development. See also /usr/lib and /usr/local/lib.

The /lib directory includes:

/lib/dll/
Contains additional shared libraries that implement OS drivers and services, such as drivers, filesystem managers, and so on. For some examples of how shared libraries are used for certain types of drivers and services, see Filesystems, and TCP/IP Networking in the System Architecture guide. For details about specific shared objects in the /lib/dll directory, see their respective entries in the Utilities Reference.