Plain English Meaning
The big chapters of your checkride. The FAA groups everything you'll be tested on into broad categories, and inside each category there are specific tasks you have to perform.
Full Definition
In the Airman Certification Standards (ACS) and Practical Test Standards (PTS), areas of operation are the major phases or subject groupings of a practical test, listed in a logical sequence that generally follows the order of a flight — for example, preflight preparation, takeoffs and landings, performance maneuvers, navigation, and postflight procedures. Each area of operation contains a set of specific tasks the must demonstrate to the examiner.