The RS-80N3 is designed to work with specific Canon bodies. Check to see which remote trigger will work on your particular camera body. Above is a photo of The Swedegon in Yangon, Myanmar, at night. It is a 0.5 second exposure. It would have been much more difficult to take this shot without a remote trigger. Even though this was shot using a tripod, it potentially would have turned out blurry without the use of a remote trigger, because of the potential camera shake from physically pressing the trigger release on the camera. You can reduce the risk of camera shake even further by going to the custom functions on your camera and enabling mirror lock up. This feature will eliminate the potential camera shake due to the cameras mirror flipping up when you trigger the shutter. If mirror lock up is enabled on your camera, the first press on the remote trigger will flip the mirror up and your viewfinder will be blacked out, but the photo will not be taken. A second press on the remote trigger is then required to tell the camera to begin recording the picture. When the shutter is released, the mirror will then flip back down and you will be able to see through your viewfinder again. This custom function works with and without the use of the remote trigger.
The remote trigger is also essential if you plan on shooting exposures longer than 1/30 of a second. At slow shutter speeds a tripod is needed, but without a remote trigger the tripod can't really do its job. For exposures down to 30 seconds it is possible to use the camera's shutter delay, but it is not ideal. For example what if you wanted to shoot some fireworks and shoot a 2 second exposure; If you try to use the shutter delay you have to hope that the fireworks will explode in the sky 3, 5, or 10 seconds after you press the shutter, depending on your camera and your delay settings. Obviously this is less than an ideal situation. In addition, if you want to shoot an exposure of more than 30 seconds you will need to use the bulb setting (when the shutter is set to bulb, the shutter will remain opened as long as you hold your finger on the shutter release button) and hold the shutter release down yourself. This is not going to work, because it will be very difficult to hold the button with you finger for extended periods without shaking the tripod and camera.
Do yourself a favor and invest $50 or so in a remote trigger. If you plan on doing any tripod work, it is an essential piece of equipment.
In addition to the RS-80N3 there are more expensive remote triggers. The RS-80N3 is the most simple model. It is basically a corded trigger that acts identically to the shutter release on the camera body. It has an additional piece that allows the trigger to be held down and not released when the shutter speed is set to bulb. There are also remote triggers that are not corded. This gives you the obvious advantage of being able to trigger the shutter from a greater distance than the corded remote trigger would allow. I personally have little use for this added function. The none corded trigger release is also significantly more expensive. Lastly, there are trigger releases that can be programmed to activate the shutter for whatever time period you want. This way you don't have to set your watch and manually release the shutter at the appropriate time. You can just set the remote trigger, walk away, and forget about it. You can also set it to take multiple pictures. This can be handy if you are taking very long exposures. If you are taking 10+ minute exposures, it can get pretty boring hanging around waiting to manual release the shutter. The only down side to these programmable trigger releases is that they run in the hundreds of dollars. For now I stick to the basic model and it does just fine for me.