The Difference Between a DSLR's Viewfinder Autofocus and Live View Autofocus
Most photographers use their cameras on a daily basis with little or no thought to how it functions under the hood. For the most part, this makes sense, mastering a tool doesn't require understanding exactly how it functions on the most intimate technical level. There are, however, aspects of camera operation that a cursory knowledge of can aid in being better equipped to address unexpected technical or mechanical issues. Given that autofocus can be finicky, it quickly becomes one of the critical aspects of your camera that you should take the time to learn about.