As nouns the difference between aga and aaa

is that aga is an alternative spelling of lang=en while aaa is initialism of lang=en.

As proper nouns the difference between aga and aaa

is that aga is a river in Zabaykalsky Krai, Russia while Aaa is alaska.

As a symbol AAA is

the highest level of minor league baseball, often used by extension in other sports to indicate the highest level of minor league play in that sport as well.

As an initialism AAA is

Abdominal aortic aneurysm