Terminating gateways are a new feature in HashiCorp Consul 1.8 that enable applications in a service mesh to securely communicate with external services outside the mesh environment, providing a consistent network and security model. They act as egress proxies, creating a single listener within the mesh that can accept connections for multiple destination services, and leveraging identities of source and target destination services to enforce Consul's access policies and intentions. By using TLS for identity and encryption, and Intentions for authorization, terminating gateways provide a common workflow for managing authentication and authorization across both internal and external services.