A technology that exposes a specific service through a private interface endpoint inside a VPC, without needing peering, without exposing traffic to the internet, and without granting access to the entire network of the service provider.
In SAP-C02 it's compared to VPC Peering: PrivateLink exposes only the specific service (more secure, least network privilege); Peering connects entire networks. Typical use case: privately consuming a third-party SaaS service without going out to the internet.
AWS PrivateLink is a concept that can show up on the exam. Check the full guide to see it in context.