Mac OS enables you to make aliases to files. It should come as no surprise that Unix does, too. But in Unix, aliases are called symbolic links. And rather than use a menu command or shortcut key to create them, you use the ln (make links) command with its -s option.
Tips
Mac OS aliases and Unix symbolic links make it convenient to access deeply buried files or to organize files differently than the way the operating system organizes them.
If you omit the -s option, the ln command creates a hard link. Hard links can't cross file systems (or partitions) and can't normally refer to directories.
Unix does not tell you if the source file to which you want to create a symbolic link does not exist. As a result, it's possible to create an alias that doesn't point to anything.
You can learn more about other options for the ln command in its man pages. Type man ln and press to display them.