If you aspire to inspire others with your love of aviation, and you have a commercial license, you can being your training to achieve a flight instructor rating. You will start out as a class 4 instructor, which requires a flight test ride and a writtent exam - the AIRAF that has 100 questions in 3 hours with a 70% pass mark. Based on achieving a set number of objectives (e.g. so many recommends), a class 4 instructor can advance to being a class 3: there is no exam for this step.
The journey to becoming a class 2 involves another ride and a written exam: the AIRAT which has 100 questions, 3 hours, 70% pass mark. The final stage is attaining the coveted class 1 instructor rating, considered as a subject matter expert and it therefore confers the priviledge of being able to instruct instructors. Same AIRAT, but with an 80% pass mark.
Whatever class of instructor you are working on, ACE helps you polish your knowledge that is now vital as you start to share this with others. ACE also caters to special situations - for example, instructing certain ratings does not necessarily require a full instructor rating. In such cases - for example if you wish to become a class 1 aerobatic instructor - you need to successful write the FITEN exam that tests learning factors and teaching methods.