Basic Syntax

note that /directory and /directory/ do different things:
/directory copies the files inside the directory
/directory/ copies the directory itself

rsync [options] source destination

common options

-r recursive
-a archive (syncs recursively and preserves symbolic links, special and device files, modification times, group, owner, and permissions.)
-v verbose
-P progress
-z compress transfer (might not be beneficial on fast connections)
--delete delete files from destination if deleted from source (normally won't delete anything)

examples

copy files from source to desination with archive and compression

rsync -azP /source/directory /destination/directory

copy and delete files (aka “mirror”) between source and destination

rsync -aP --delete /source/directory /destination/directory

copy files from local source to ssh:destination

rsync -a /source/ username@remote_host:destination

copy files from ssh:source to local destination

rsync -a username@remote_host:/source /destination