Working with Symbolic Links

First command (ls -F) plus outputL: This command simply displays the directory contents before you create the link.
Second command (ln -s): This command takes the first file name, project/qa/test_plan.html and creates a symbolic link to it. The link will be named qa.html.
Third command (ls -F) plus output: The directory now contains a symbolic link named qa.html. The -F option appends an character to help identify the link.
Fourth command (ls -lF) plus output: The ls -l output uses an arrow (->) to reveal the actual file, which the qa.html link points to. Note the access mode. The file type field, the leftmost character, shows the letter l, which stands for link.

Link Files

The concept of a link in UNIX is for file sharing. A link file is created by the system when a symbolic link is created to an existing file. The link file points to the existing file, which allows the users to rename an existing file and share it without duplicating its contents. As introduced in Section 6.1.4, for the kernel, every file has one inode, but it may have several names of links, all of which map into the inode. The concept of the symbolic link in UNIX is a creation of BSD but is presently available on almost all versions of UNIX (Ousterhout et al 1985; Quarterman et al 1985). The symbolic link is also called soft link. A symbolic link may be a file containing the pathname of another file or directory, and it can cross file system boundaries. In contrast to soft link, it is a hard link.
There are two typical hard links:

one is written as '.'; the other is '..' .
'.' in a directory is a hard link to the directory itself, and '..' of the directory is a hard link to its parent directory.