At this point, we’ve covered how to create the entities within the plugin (which, as we’ve said, is just a fancy word for another concrete idea). Namely, we’ve got a user and a custom post type, or a book. And here’s where we start to take the two separate entities and combine and work with what we’ll call WordPress metadata association.
But before doing so, it’s important to understand the two types of metadata with which we’ll be working and the two ways (or three ways, depending on how you look at it) in how we can associate the metadata.
As with the rest of the posts in the series, this isn’t meant to be a deep-dive into understanding each of the tables or a deep-dive into each of API functions. Instead, we’re going to survey what’s available, put them to use, and leave finer details for future posts (or perhaps discussions in the comments).