Show run, shows the running config. It shows every command that is active on router and that may not have been saved yet. If you only have running config (not saved) and you boot the router, you will lose that config.
Show config gives you what is saved in NVRAM. You can also use more nvram:startup-config
For command look-ups, you can simply go to the following link and type in the command you need help with:
http://www.cisco.com/cgi-bin/Support/Cmdlookup/home.pl
Thanks.
