Symbolic link (symlink)
A small file containing a path, resolved on every access.
A symbolic link is a tiny file whose content is a path to something else. Every time you open it, the system reads that path and follows it. Because it stores a path rather than a reference to an inode, a symlink can cross filesystems, point at directories, and even point at something that does not exist yet: a "broken" link.
Symlinks power two ubiquitous patterns: dotfiles kept in a git repo and linked into place, and deployment schemes where /opt/app/current points at the active release, so switching versions is one atomic link change.
See it in practice
$ ln -s /opt/app-2.4.1 /opt/app/current && readlink -f /opt/app/currentCreates a pointer and then resolves it. Switching releases is one atomic link change.
Where you'll meet it
Make one file reachable from several paths, and understand symlinks vs hard links.
Hard linkA second, equally real name for the same file.
InodeThe structure that IS a file: metadata plus pointers to its data.
Errors that come down to this concept: No such file or directory