`protoc-gen-grpc-gateway` generates a few public functions which you can use to bind your service to grpc-gateway. You can, - pass a gRPC client instance, - pass a gRPC connection, - pass a gRPC endpoint in string format, - pass a gRPC service instance implementing the service interface generated by `protoc-gen-go-grpc`.

These are meant to fit grpc-gateway to scenarios where gRPC server might be implemented in another programming language, or accepting clients at a TCP port or another kind of a socket, possibly under a different network realm than grpc-gateway. Pretty much like a reverse proxy, but can also be integrated with services in the same code level, escaping the overhead of a transport layer.