Yes. This is αυτός ο for masculine nouns, αυτή η for feminine nouns and αυτό το for neutrum nouns.
Duolingo pronounces "τρως" something like "tribos." Why does it have a b sound?
You really hear a "b" sound in it: https://www.duolingo.com/dictionary/Greek/%CF%84%CF%81%CF%89%CF%82/bbad7442ede86d7268f993eb22c8b212 ?? I just hear "tros" with a rolling, Greek r.
I didn't hear the same thing in other questions with "τρως" but in this one I did.
How can one tell when τρως means "you eat" and when it means "you are eating"?
Greek doesn't distinguish between present and present continuous. You can maybe work out from context more specifics regarding the action but it's not a distinction that matters.