This type of shortcut is the oldest for the Mac; its roots go all the way back to System 7. Aliases are created and managed at the Finder level, which means that if you’re using Terminal or a non-Mac application, such as many UNIX apps and utilities, an alias won’t work.
This type of shortcut is part of UNIX and Linux file systems. Because OS X is built on top of UNIX, it fully supports symbolic links. Symbolic links are similar to aliases in that they are small files that contain the pathname to the original object. But unlike aliases, symbolic links don’t contain the inode name of the object. If you move the object to a different location, the symbolic link will be broken, and the system won’t be able to find the object.
Like symbolic links, hard links are part of the underlying UNIX file system. Hard links are small files that, like aliases, contain the original item’s inode name. But unlike aliases and symbolic links, hard links don’t contain the pathname to the original object. You would typically use a hard link when you want a single file object to appear in multiple places. Unlike with aliases and symbolic links, you can’t delete the original hard-linked object from the file system without first removing all hard links to it.