The YN-622c triggers can't be used as shutter releases. Don't get the cable if you're getting the 622c set. Also, that cable is for the YN-602 triggers, not the YN-603. If you get the 602s or 603s, they'll come with a shutter release cable, so that's why the previous posted told you to select the one specific for your camera (the dRebels use a 2.5mm minijack port for the shutter release--higher-end Canon bodies don't, so they need a different cable.)
The YN-622c triggers give you far more than just eTTL, btw. They communicate the full hotshoe protocol between the camera and the flash. So you can command the remote flash via your camera's flash control menu. As you can control the power settings on your remote flashes without having to walk up and dial it in. This is the main reason we like the 622s over the manual triggers.
In addition to eTTL, you will also have access to high-speed sync, rear-curtain sync (with wireless turned off), nearly every setting possible on the flash (zoom, custom functions, etc.) from your camera. Highly recommend reading Cliveyboy's "other" guide to the 622s to get an idea as to why they're worth the higher pricetag over the 603s, aside from locking rings on the feet and eTTL.