There exist relays of different types which use up a lot of resources, instead of providing them directly 88.io provide directories of these relays for easy reference.
TURN Relay
TURN enables WebRTC traffic (e.g. audio, video etc.) to be relayed between WebRTC clients that cannot be connected directly with each other - even with the help of STUN servers e.g our own stun.88.io.
Activitypub Relay
Activitypub Relay enables activitypub servers to see many more
Relay protocols supported must be supplied when listing on a directory. Support of both Mastodon relay (/inbox) and Pleroma relay (/actor) is preferred.