A Service gives your Pods a stable network identity. Since Pods are ephemeral and their IPs change when they restart, you need something consistent to point at. That’s what a Service does. It provides a single DNS name and IP that routes traffic to the right Pods using label selectors.
There are different Service types: ClusterIP (internal only, the default), NodePort (exposes on each node’s IP at a static port), LoadBalancer (provisions an external load balancer in cloud environments), and ExternalName (maps to a DNS name outside the cluster).