Partner Events publishers create a registration to enable a first-party experience through which users can create partner topics you define. A Partner Registration mainly describes the following:

• The resource (partner topic) type that users see on Azure portal’s Event Grid Create Partner Topic. Each Partner Registration defines a type of partner topic. Hence, it is possible to define more than one type through additional Partner Registration instances.
• The URI to a web page an Event Grid partner hosts that provides the ability for users to create a partner topic.
• The general contact information for a user to get support from you (an Event Grid partner) when issues or questions about the partner topic type you are defining.