What is the difference between hard link and soft link in Unix/Linux?

A hard link in Unix/Linux is a direct link to an inode (data structure representing a file) on the disk. When a hard link is created for a file, it points directly to the inode of the original file. Changes made to the original file will be reflected in all hard links pointing to it. Hard links cannot cross filesystem boundaries, and cannot link directories.

A soft link, also known as a symbolic link, is a pointer to the filename of a file. Unlike a hard link, a soft link points to the pathname of the original file rather than the inode itself. If the original file is deleted, the soft link will break and become unusable. Soft links can point to directories and can cross filesystem boundaries.