The 603s will create a wireless connection between the cameras hotshoe and the flashes foot.
Something you don't mention though is the flash you are considering. I ask because the 603s will only transmit "manual" flash information and not TTL (Through The Lens) metering information. I'd assume that if you are looking at YN603 triggers that you are also looking at Yongnuo flashes and probably the YN560 II, which is a manual flash (you input the settings), however, if you're looking at something with TTL then you'd need to find a trigger that will transmit that information to the flash or you're wasting your money.
Personally, I'd recommend buying the 603s and YN560 II, it's a cheap setup and you'll learn more than just letting it all be decided for you, it's what I did!