-L Display the logical current working directory.
-P Display the physical current working directory (all symbolic links resolved).
If no options are specified, the -L option is assumed.
In Bash and many modern POSIX shells, `pwd` is a builtin, not to mention an environment variable ${PWD}, but the POSIX system should also provide an external command, such as `/bin/pwd` that would operate on the filesystem, rather than semantically tracking your shell activity.