The most confusing thing about rsync for me is that a trailing slash is important (meaning "copy the contents" rather than "copy the directory"), so the following two commands do the same thing:
rsync -av /src/foo /dest rsync -av /src/foo/ /dest/foo
To use rsync over the network , bascially you just need to let it know that it should transfer files over ssh. Something like this from the current machine to synapse (remove the --dry-run to transfer for real):
rsync --dry-run -v -az -e ssh testdir email@example.com:temp
You can also get all fancy and tell ssh what cipher to use like this:
rsync --dry-run -v -az -e "ssh -c blowfish" testdir firstname.lastname@example.org:temp
blowfish is supposed to be quite a bit faster but machines are so fast these days that I doubt it will matter except when transferring gigabytes of files.