If something is not in your $PATH, and you don't give it a full path, it won't know where to find it.
[z@z ~]echo $PATH
Anything that is /not/ in one of those directories won't run, unless you specifiy the full path:
[z@z ~]cp /bin/ls /tmp/somecommand
-bash: somecommand: command not found
(normal 'ls' output here)
Running 'somecommand' didn't work, because it is not in my $PATH, so I had to give it the full path. Does this help?