PostgreSQL provides several facilities to interact with processes, either internal or external to the server. One important facility is the IPC layer built on top of events and channels, which allows applications and database connections to exchange information through asynchronous events. Another important feature is the Background Worker layer, which enables developers to plug their own specific custom processes into the server.
In the next chapter, we will learn how to add a custom data type to the already rich set provided to you by PostgreSQL.