pgAdmin 4 is a client application that sends and receives SQL to PostgreSQL, displaying the results for you to browse. One pgAdmin client can access many PostgreSQL servers, and a PostgreSQL server can be accessed by many pgAdmin clients.
pgAdmin 4 is usually named just pgAdmin. The "4" at the end has a long history, but isn't that important. It is not the release level; the release level at the time of writing this book is 1.1. pgAdmin 4 replaces the earlier pgAdmin 3.
When you start pgAdmin, you will be prompted to register a new server, as shown in the following screenshot:
Give your server a name on the General tab, then ...