Minecraft wiki entry for Mac_Scripting_Tutorial, associated text: --delete removes files on the destination that have been removed on the source, which helps keeps clutter to a minimum
--force ensures that directories that have been removed on the source get removed on the destination, again helping to keep clutter down
-aPe is three options lumped into one:
a tells rsync to use its "archive" preset, which basically tells rsync to copy all the subdirectories within the directory you're copying, and to preserve the layout and attributes of the files.
P tells rsync to keep partially-transferred files, and also to display a progress indicator as the copy runs, so you have something to look at if you happen to be at your computer while the script is running
e ssh tells rsync that it's going to use ssh on the remote computer to execute commands
--exclude 'Cache' makes rsync skip copying over the Tectonicus cache directory. The cache directory can be very large and contain hundreds of thousands of files, so not transferring this to the web server can save a lot of time.
$TECTOUTPUT/* $WEBSVC@$WEBSERVER:$WEBSERVERPATH tells rsync to copy the Tectonicus output directory to the desired destination path on the web server, logging on with the account you specified. The values you put in the variables section at the beginning are substituted in when the command is run by the script.