From LXF Wiki
A symlink, or symbolic link, is a small file that acts as a placeholder, and points somewhere else on the filesystem. Symlinks are useful for creating shortcuts to programs and directories.
For example, if you replace the traditional lp tool, you can create a symlink from lp to the new command and (providing it accepts similar input) any systems or users will still be able to use the old command.
Symbolic links are created with the ln command.