Another handy command is "whereis"
> whereis ifconfig
If you need to access a program that isn't in your PATH, add it by editing $HOME/.bash_profile
Finally, you can use "find" a command or file.
>find / -name "file_name" - will search / (root) for file_name - note that unless you run this as the user root you'll get "permission denied" errors.
To get help with commands, try man <command_name> . "man" is short for manual, and will bring up a manual page for the command and any configuration files that accompany it, as well, usually, as it's normal location.