The relayer binary is designed to connect to two chains, create a connection if needed, create channels on demands, and relay a selected subset of packets between the two chains. It is designed to run on a secure machine and must be provided with a funded account on each chain. If you wish to connect multiple chains, please run one (or more) relayer for each pair you wish to connect.
Informal systems provides a good overview of a relayer in their ibc-rs repo. This image is borrowed from there.
We have split the relayer into 2 binaries for two different use cases, to ensure we cover both cases best:
ibc-setup- this is an interacticve admin tool, used to create keys, setup clients and connections, and any other one-time tasks run by a human.ibc-relayer- this is designed to run as a daemon (service), controlled by env variable and config files and with instrumentation (logging, metrics, etc) fit for running unattended in a production environment.