The remote username used is the same as your local username, unless you specify a different remote name with the -l option. This remote name must be equivalent (in the sense of rlogin(1C)) to the originating account; no provision is made for specifying a password with a command.
If you omit command, then instead of executing a single command, you will be logged in on the remote host using rlogin(1C).
Shell metacharacters which are not quoted are interpreted on local machine, while quoted metacharacters are interpreted on the remote machine. Thus the command
rsh otherhost cat remotefile >> localfile
appends the remote file remotefile to the localfile localfile, while
rsh otherhost cat remotefile ">>" otherremotefile
appends remotefile to otherremotefile.
Host names are given in netinfo(5) if NetInfo is running or in the file /etc/hosts if NetInfo is not running. Each host has one standard name (the first name given in the file), which is rather long and unambiguous, and optionally one or more nicknames. The host names for local machines are also commands in the directory /usr/hosts; if you put this directory in your search path then the rsh can be omitted.
netinfo(5)
You cannot run an interactive command (like rogue(6) or vi(1)); use rlogin(1C).
Stop signals stop the local rsh process only; this is arguably wrong, but currently hard to fix for reasons too complicated to explain here.