Start here. This is the direct spoken answer to practice first.
Why this question matters
Compare public and internal APIs in terms of compatibility, documentation, security, support, and evolution speed. It matters in real backend work because release traceability, quality gates, and rollback options decide whether changes can move safely through environments. The practical angle is contract stability, documentation, compatibility, support processes, security, and release coordination, tied to a concrete production decision.
For a public API, I am stricter about contract stability, documentation, versioning, error shapes, authentication, rate limits, and backward compatibility. Internal APIs can sometimes evolve faster because the consumers are known. That does not mean internal APIs can be sloppy, but the risk profile is different. Public clients cannot always update on our schedule.