GitHub associates a unique resource ID (or "database ID" or just "ID") with each
API-accessible resource. For example, each [issue][issue-id],
[repository][repository-id], and [user][user-id] has a global ID. In my limited
experience with it, GitHub's REST API generally does not expose endpoints by
which resources can be queried by ID (though it does have some [undocumented
endpoints][repo-rest]). These resource IDs have been superseded by distinct
[global node IDs][global-ids] (node_id). GitHub's GraphQL API allows retrieval
of a node by its ID, called a "direct node lookup".
As you can tell, you likely don't have much reason to interact with the older