MeaningA special word that comes before a person or thing that is getting an action. It shows that the action is done *to* that specific person or thing. English does not have a word like this.
HistoryThis is one of the most common words in Hebrew. It appears thousands of times in the Bible. Its job has always been the same: to point to the specific person or thing that receives the action in a sentence.
Exampleאני אוהב את הכלב שלי.
I love my dog.