if you tap on the AC icons it will tell you what they are. if you tap the symbol on the bottom right (3 panel image) of the screen, it will bring up chart contents...tap on AC and it lets you customize what is shown on the chart. Marina's, anchorages, hazards, and local knowledge. you select all of them, none of them (that's how I turn it off) It is nice you can pick and choose. I have limited knowledge on this program, so perhaps Larry can step in and go more into depth. For $30 bucks it's great when it works.