What are hard and soft links?

The mapping within a directory list that defines the name of a file and it’s i-node number is called a link, or a hard link. One can create multiple names — in the same or in different directories — each of which refers to the same i-node.
Hard links have two limitations, both of which can be circumvented by the use of symbolic links:
* Because directory entries (hard links) refer to files using just an i-node number, and i-node numbers are unique only within a file system, a hard link must reside on the same file system as the file to which it refers.
* A hard link can’t be made to a directory. This prevents the creation of circular links, which would confuse many system programs.
A symbolic link is just a file containing the name of another file; Symbolic link refers to a file name, rather than an i-node number, it can be used to link to a file in a different file system.