reviewapp-operator works in concert with the Argo CD to realize "launching a new environment for development (as Review Apps environment) when any PullRequest is opened in the application-repository".
reviewapp-operator is mainly responsible for "creating and deleting manifests to the manifest-repository when PullRequests in the application-repository are updated," and Argo CD is responsible for actually applying the manifests from the manifest-repository to Kubernetes.
please read Release