You can think of relays like e-mail servers. You may be on the gmail.com relay, another person on the outlook.com relay, but you can both send messages back and forth to each other. Most apps connect to several relays by default. Which relays you are connected to determines what is in your "global" feed, which is curated by your app into "trending" or whatever other sections it may have. As long as you have one working relay, you are good, most users never need to modify their relay list and this is aok.