These are used to toggle on/off that relay for a particular feed. From left to right, it's for

-Home feed

-DMs

-Groups/Channels (like this Amethyst users)

-Global feed

-Search (not many relays support this. Currently only nostr.band)

If it's green that relay is on for that activity, grey if not.

Down Arrow (read from): count gives # of notes read from that relay

Up arrow (write to):

# of notes posted to that relay from your account

(!): Error count

🗑️: Spam count