Just adding the official Kubernetes documentation about creating a service:

https://kubernetes.io/docs/concepts/services-networking/service/

A Service in Kubernetes is a REST object, similar to a Pod. Like all of the REST objects, a Service definition can be POSTed to the apiserver to create a new instance. For example, suppose you have a set of Pods that each expose port 9376 and carry a label "app=MyApp".

kind: Service
apiVersion: v1
metadata:
  name: my-service
spec:
  selector:
    app: MyApp
  ports:
  - protocol: TCP
    port: 80
    targetPort: 9376

This specification will create a new Service object named “my-service” which targets TCP port 9376 on any Pod with the "app=MyApp" label. This Service will also be assigned an IP address (sometimes called the “cluster IP”), which is used by the service proxies (see below). The Service’s selector will be evaluated continuously and the results will be POSTed to an Endpoints object also named “my-service”.

Note that a Service can map an incoming port to any targetPort. By default the targetPort will be set to the same value as the port field. Perhaps more interesting is that targetPort can be a string, referring to the name of a port in the backend Pods. The actual port number assigned to that name can be different in each backend Pod. This offers a lot of flexibility for deploying and evolving your Services. For example, you can change the port number that pods expose in the next version of your backend software, without breaking clients.

Kubernetes Services support TCP and UDP for protocols. The default is TCP.