- It can change the data stream which would go to a file to the stdout.
- It can import the data stream which would come from a file from the stdin.
tar -cvf - /home | tar -xvf -
This shell command result is same as the command
mv /home/* ./
The data which would go into a archive is now going to the stdout, then use the pipe to change the stdout as stdin, then use the symble '-' to import the stdin data stream into the 'tar -xvf' command to extract them to now using folder.