"I see the food."
Translation:אני רואָה את האוכל.
Maybe the sentence was changed since this comment? Because what I see here is correct. I see the food, אני רואה את האוכל. The את marks a definite direct object.
The translation here is incorrect. The word את here is pronounced "et". It is not the same word as את ("aht") which means "she". It is used to mark the object of the sentence. Report that next time you see this.
We use את when BOTH these things are true:
1) The word is the direct object of the sentence. In other words: it is receiving the action of the verb. It is being seen, eaten, read, created, etc.
2) This word is ALSO definite/specific. It is not just food in general, but specifically THE food being eaten. Not just a book (any book in general), but specifically THE book being read. Proper nouns are also definite and require את. Duo will introduce other instances later in the tree :-)