How do I know what a pod is doing?

kubectl -n <NAMESPACE> describe pod <POD>

You can find out the current status of a pod

>kubectl -n kube-system describe pod coredns-558bd4d5db-trkcv
Name:                 coredns-558bd4d5db-trkcv
Namespace:            kube-system
Priority:             2000000000
Priority Class Name:  system-cluster-critical
Node:                 docker-desktop/192.168.65.4
Start Time:           Sun, 11 Jul 2021 15:14:58 +0100
Labels:               k8s-app=kube-dns
pod-template-hash=558bd4d5db
Annotations:          <none>
  Status:               Running
  IP:                   10.1.0.3
  IPs:
  IP:           10.1.0.3
  Controlled By:  ReplicaSet/coredns-558bd4d5db
  Containers:
  coredns:
  Container ID:  docker://82953fdb273a558f20000b9e3d096ba2d63ef686fdad62fb048c011938fd6557
  Image:         k8s.gcr.io/coredns/coredns:v1.8.0
  Image ID:      docker-pullable://k8s.gcr.io/coredns/coredns@sha256:cc8fb77bc2a0541949d1d9320a641b82fd392b0d3d8145469ca4709ae769980e
  Ports:         53/UDP, 53/TCP, 9153/TCP
  Host Ports:    0/UDP, 0/TCP, 0/TCP
  Args:
    -conf
    /etc/coredns/Corefile
  State:          Running
    Started:      Sun, 11 Jul 2021 15:15:00 +0100
  Ready:          True
  Restart Count:  0
  Limits:
  memory:  170Mi
  Requests:
  cpu:        100m
  memory:     70Mi
  Liveness:     http-get http://:8080/health delay=60s timeout=5s period=10s #success=1 #failure=5
  Readiness:    http-get http://:8181/ready delay=0s timeout=1s period=10s #success=1 #failure=3
  Environment:  <none>
  Mounts:
  /etc/coredns from config-volume (ro)
  /var/run/secrets/kubernetes.io/serviceaccount from kube-api-access-bl5jw (ro)
  Conditions:
  Type              Status
  Initialized       True
  Ready             True
  ContainersReady   True
  PodScheduled      True
  Volumes:
  config-volume:
  Type:      ConfigMap (a volume populated by a ConfigMap)
  Name:      coredns
  Optional:  false
  kube-api-access-bl5jw:
  Type:                    Projected (a volume that contains injected data from multiple sources)
  TokenExpirationSeconds:  3607
  ConfigMapName:           kube-root-ca.crt
  ConfigMapOptional:       <nil>
  DownwardAPI:             true
  QoS Class:                   Burstable
  Node-Selectors:              kubernetes.io/os=linux
  Tolerations:                 CriticalAddonsOnly
  node-role.kubernetes.io/control-plane:NoSchedule
  node-role.kubernetes.io/master:NoSchedule
  node.kubernetes.io/not-ready:NoExecute for 300s
  node.kubernetes.io/unreachable:NoExecute for 300s
  Events:
  Type     Reason     Age                    From                     Message
  ----     ------     ----                   ----                     -------
  Normal   Scheduled  6m12s                  default-scheduler        Successfully assigned kube-system/coredns-558bd4d5db-trkcv to docker-desktop
  Normal   Pulled     6m10s                  kubelet, docker-desktop  Container image "k8s.gcr.io/coredns/coredns:v1.8.0" already present on machine
  Normal   Created    6m10s                  kubelet, docker-desktop  Created container coredns
  Normal   Started    6m10s                  kubelet, docker-desktop  Started container coredns
  Warning  Unhealthy  5m42s (x4 over 6m10s)  kubelet, docker-desktop  Readiness probe failed: HTTP probe failed with statuscode: 503