To be more specific, you use the "link" command,
ln. As with most all commands/programs, you can use
ln --help or
man ln to get more information, but the main thing to know is that there are two types of links, hard links and symbolic (soft) links.
Symbolic links, using the
-s switch, are like windows shortcuts. You create a shortcut to the actual file, and if you delete the file, the link becomes invalid.
Hard links, the default, create a new entry for the file. The main thing to know here is that although they both use the same actual data, each one is somewhat independent. If you delete one, the other is still valid. Basically, the file has a link count, and the actual data does not get deleted until all the links are deleted.