Note: examples that use a shell use ssh

To synchronize a local directory with a remote one, use:

rsync -r -a -v -e "ssh -l username" --delete hostname:/remote/dir/ \
/local/dir/

To synchronize a remote directory with a local one, use:

rsync -r -a -v -e "ssh -l username" --delete /local/dir/ \
hostname:/remote/dir/

To synchronize a local file with a remote one, use:

rsync -a -v -e "ssh -l username" hostname:/filename /local/filename

To synchronize a remote file with a local one, use:

rsync -a -v -e "ssh -l username" /local/filename hostname:/filename

To synchronize a local directory with a remote rsync server:

rsync -r -a -v --delete rsync://rsync-server.com/stage/ /home/stage/

To synchronize a local directory with a local directory (make a backup), use:

rsync -r -a -v --delete /local/dir/ /backup/dir/