OpenShift 4 introduced several significant changes and new features compared to OpenShift 3. Some key differences and new features in OpenShift 4 include:

1. Operator Framework: OpenShift 4 introduced the Operator Framework, which is a method for packaging, deploying, and managing Kubernetes applications. Operators automate common operational tasks such as deployment, scaling, and backup/restore. This framework enables more efficient management of complex applications.

2. Operator Lifecycle Manager (OLM): OLM is a component of the Operator Framework that helps manage the lifecycle of operators. It facilitates the installation, upgrade, and management of operators in an OpenShift cluster, making it easier to maintain and update applications.

3. Self-Managing Control Plane: OpenShift 4 introduced a self-managing control plane, which automates various operational tasks related to the management of the cluster's control plane components. This includes automated updates, scaling, and self-healing capabilities, reducing the operational burden on administrators.

4. Improved Installer: The OpenShift 4 installer has been redesigned to provide a more streamlined and user-friendly installation experience. It uses a declarative model for cluster configuration and supports various installation platforms, including bare metal, virtualized environments, and public clouds.

5. Integrated Prometheus Monitoring: OpenShift 4 includes Prometheus as the default monitoring and alerting solution, integrated with the cluster's monitoring stack. This provides built-in visibility into the health and performance of the cluster and applications.

6. Quay Container Registry: OpenShift 4 includes Red Hat Quay as the default container registry. Quay is a scalable container image registry that provides features such as security scanning, vulnerability analysis, and container image promotion.

7. Automated Day 2 Operations: OpenShift 4 simplifies day 2 operations with features such as automated cluster updates, application lifecycle management, and built-in GitOps workflows. These capabilities help streamline the ongoing management and maintenance of OpenShift clusters.

These are just a few of the key differences and new features introduced in OpenShift 4 compared to OpenShift 3. Overall, OpenShift 4 focuses on enhancing automation, scalability, and ease of use, making it easier to deploy and manage Kubernetes-based containerized applications