trickykid answered that question. maybe you didn't actaully read his reply. your current directory is not on your path as there is no conventional reason for this. when you type a command, you will typically be running a program that is installed in your system and on your path. the exception we have in your case is that you are writing your own code, so the program is not installed. if you really want you can add . (the current directory) to your path, but it's not advised, as you could easily get into many daft situations you're just not aware of at the moment.
personally i'm also developeing a program,
http://acidrip.thirtythreeandathird.net and it is insatlled on my system, so when i run "acidrip" it runs the installed version. Now, i am still writing it as wel, asnd obviously don't wish to get the developement version confused with the installed one. if my working directory was on my path, then i wouldn't necessarily know which version i was running, however specifying the relative path "./acidrip" means i know what i am running, and i am in control.
you may not quite get the hang of it yet, but it all makes sense when you get used to it. conventions are tehre for a reason.
