links

# ls -il /etc/hosts
-l long listing and -i is inode
# ln sourceFile destinationFile
# ln /etc/hosts computers
symbolic:
# ls -s sourceFile destinationFile
# ls -s /etc/hosts computers
On soft links the permissions are differents and in pointing to another inode.
Normal user cannot create hard links for /etc/shadow.
Can link to files where you have at least READ permissions.