How does the patroni postgres cluster work?

Question

PostgreSQL

There is an application, the server on which is patroni (arbitrator), and 2 servers from the database. How does patrony work? He has in the settings who is the master, who is the slave, and he makes a replica from the master to the slave. And in a java application, in the jdbc connection string, 2 servers with a database are indicated, and how does he understand who is the master and who is the slave and with whom to connect? It's just that in my understanding it was necessary to connect to the arbiter and it redirects which server to interact with. Explain how the logic works?