People have two different definitions for serverless in the cloud, especially in the context of Kubernetes. The first meaning is that you don't have to manage the nodes for your cluster. Some good examples of this concept include AWS Fargate (https://aws.amazon.com/fargate/) and Azure Container Instances (ACI) (https://azure.microsoft.com/en-us/services/container-instances/). The second meaning of serverless is that your code is not deployed as a long-running service, but is packaged as a function that can be invoked or triggered in different ways on demand. Some good examples of this concept include AWS Lambda, and Google Cloud Functions.
Let's understand the commonalities and differences between services and serverless functions.