Lets say you want to play with your friend, but the server filled up before you got in or perhaps you are only looking for a 7v7 objective in a certain area for your ping is not through the roof when you quick match
All you need to do is Favourite the server or group of servers and then you have a smaller list to refresh rather then having to wait for all the servers to load and then sort through them again.
Done with the server, just remove it from your favourites and you are good to go