What are treats?

They're just votes by other participants on this board and reflect good questions and answers. They are explained in the FAQ linked above:

https://www.rover.com/community/faq/

There are pluses and minuses next to each question and answer and you can vote on them. The person asking the question can also formally accept an answer as correct, which awards treats.

It isn't a game or contest sponsored by Rover where you win anything, except perhaps self-satisfaction.