From documentation: At Facebook's core is the social graph; people and the connections they have to everything they care about. The Graph API presents a simple, consistent view of the Facebook social graph, uniformly representing objects in the graph (e.g., people, photos, events, and pages) and the connections between them (e.g., friend relationships, shared content, and photo tags). Public information can be accessed without a developer key/application key, but is required for private data access.
The Facebook Graph API has since undergone numerous versioning updates. Launched in July 2016 and scheduled to last until at least July 2018, the newly integrated features of version 2.7 include: new metrics for pages, new Webhooks field, and geotargeting support for videos. The other advancements that differentiate the v2.7 from v2.6 include: the requirement of separate permissions for the Business Manager API, accommodation of additional data in the returns of posts for tagged pages, and the requirement of explicit specification of page metrics for requests that concern page insights. There are also many other updates to the budget logic, ad placements, and insights placement settings of the version’s marketing functionality. All these changes are accessible in the documentation of the API.