Relays are not very different from Wave Breakers.
Relays are usually built in High Orbit and then moved to their destination by a wave Breaker.
Some Relays are even Wave Breakers that have damaged engines, though they don't grip onto their surroundings like a regular Relay their engines work well enough to stabilize them.
A Relays job varies from construction, recreation, domiciles, a pitstop for Runners, or research and development.
The Blue Fleet has even made personal Relays that can have as little as one crew member. These are closer to Planetside crafts than Wave Breakers or Robios