Feed events are posts you see in your feed. They have three main components:
Audience
The audience of a feed event is who will receive it. This can be a list of users or teams or both. You specify the audience for a feed post with the user_ids or group_ids field.
Category
This is the kind of event that you are sending. You specify a list of category ids and a description of what they are when configuiring your integration. Every feed event your integration sends must specify what category it is in the category field. Users of your integration can configure which categories of event they want to receive from your integration.
For example, your integration may have a 'dailySummary' category which are feed events your integration sends at 9am every day and a 'eventAlert' category which are feed events that are sent when a certain event happens in your external system. If a user only wishes to receive 'eventAlert' posts, they'll be able to specify they don't want to receieve 'dailySummary' posts on the manage integrations page.
Body
This is how you specify how the feed event appears in users feeds. The body field is a JSON string containing a CardKit card. CardKit cards are JSON objects that adhere to the Blink CardKit spec and are very flexible, allowing you to build cards that meet the needs of your integration and present information clearly to your users.