Can you explain what the term 'request' means in the context of Kubernetes?

In Kubernetes, the term "request" refers to the resource that a container or pod requests from the system for its operation. This is the minimum amount of resources (such as CPU or memory) that the container is guaranteed to receive upon startup.

For example, if a pod manifest specifies:

resources:
  requests:
    memory: "128Mi"
    cpu: "500m"

This means Kubernetes will allocate at least 128 megabytes of memory and 0.5 CPU (half a core) to the container to ensure its operation. If there are not enough resources in the cluster to satisfy these requests, the pod will not be started.

The difference from "limits" is that limits are the maximum resources a container can use, while requests are the guaranteed minimum.