A function is a serverless workload type which is provided by the project "Kyma" through an custom resource (CR). "Serverless" does not mean that there is no server or infrastructure involved. It simply means that the server is managed by a third party and you do not have to worry about it. You can focus on the code of your function.
Technically, Functions in Kyma relies on multiple Kubernetes resources such as Deployments, Services, HorizontalPodAutoscalers, and Jobs.
So in terms of serverless functions in Kyma, you can simply run code snippets without providing and maintaining the container image or the infrastructure. And like deployments based on containers, functions can also be scaled , exposed and subscribed to events.