What does "down" mean in this sentence?
"Down at [place]" is an informal expression only used when speaking. It means "at" and is usually used to refer to a past event at a specific location. It can be used to indicate distance from the speaker, although often it is just an extra added word that does not actually have any special function of its own. A word that is similarly used is "back at [place]." Ex: Back at school, I saw my teacher secretly watching Netflix in the classroom. Ex: Down at McDonald's, I spotted a celebrity eating a cheeseburger.