The table of contents for pages on autofocus, from here you get to practical tips on autofocus operation and background knowledge on how autofocus works.
Autofocus – how it works
The different types of autofocus explained: phase detection, contrast detection, hybrid autofocus. What technology is behind it, which camera types use what type of autofocus and what are their advantages and disadvantages.
The most important autofocus settings answer two questions: What point in the image is your camera targeting for focus? And should it constantly adjust the focus to follow a moving subject? This page introduces you to both.