rsync <options> /from/folder/path user@host:/path/to

Note about paths: /from/folder/path means send the whole folder, where as /from/folder/path/ means send just the contents of the folder.

If you want to send ~/sync so it ends up into ~/sync on the other computer then use: rsync -a ~/sync user@host:

The syntax is like that of scp

Common Options:

-a does recursive (so no need for r)

-P Shows progress and allows you to resume interrupted transfers.

--checksum verify checksum (currently MD5) when the time and filesize matches

-v for verbose

-n for dry run

-z compresses the transfers

More Info