The A-Ok symbol is a way to visually indicate that something is fine, okay, or just right. Typically, this symbol will be used as a form of evaluation or review. For example, if you ask a boss or supervisor how a certain design or document layout looks, they might save some time and give you the “A-Ok” symbol instead of a drawn out explanation. Or maybe you’re trying to fix a car problem and you need a way to show your buddy sitting in the driver seat that everything looks good, but you can’t hear anything over the roaring engine.
Pretty self-explanatory stuff. On the other hand, this symbol means much more offensive things in places such as Venezuela, Turkey, and Brazil, so be careful how and where you use it.