I have used Back Button Focusing for a long time now. What is it? Well, instead of using your shutter button to obtain focus, you assign one of the other buttons on the back of your camera. It also means that you don't have to remember to switch over to manual focus in certain scenarios because, as long as you don't touch the assigned button, your focus was locked when you used the back button. This means that when you use the shutter button to take the photo, your camera lens will not start 'hunting' for something to focus on. Really handy when you are using hyperfocal distance to make sure your landscapes are in focus front to back irrespective of focal length and aperture.
The other advantage is when you combine Back Button Focusing with Al Servo mode (Canon terminology), then as long as you keep the back button pressed, your lens will track the subject and keep it in focus.
Check out this video that I found on YouTube - the chap shows you how to set your camera up.