Enforcing entity loader. All loads through this loader are guaranteed to be the values of successful results (or null for some loader methods), and will throw otherwise.
Entity loader utilities for things like cache invalidation, entity construction, and authorization. Calling into these should only be necessary in rare cases.
Authorization-result-based entity loader. All loads through this loader are are results (or null for some loader methods), where an unsuccessful result means an authorization error or entity construction error occurred. Other errors are thrown.
The primary interface for loading entities. All normal loads are batched, cached, and authorized against the entity's EntityPrivacyPolicy.