What does f: and k: in my YAML files indicate?

Hi,
I was woundering what the entries starting with f: and k: in my YAML files indicate or simply put what are they?
Here is an exampe:
"
apiVersion: batch/v1
kind: Job
metadata:
creationTimestamp: "2021-04-12T10:18:47Z"
labels:
controller-uid: 915a9383-e101-41cc-957f-2061a326e8e9
job-name: sleepy
managedFields:
- apiVersion: batch/v1
fieldsType: FieldsV1
fieldsV1:
f:spec:
f:backoffLimit: {}
f:completions: {}
f:parallelism: {}
f:template:
f:spec:
f:containers:
k:{"name":"resting"}:
.: {}
f:args: {}
f:command: {}
f:image: {}
f:imagePullPolicy: {}
f:name: {}
f:resources: {}
f:terminationMessagePath: {}
f:terminationMessagePolicy: {}
f:dnsPolicy: {}
f:restartPolicy: {}
f:schedulerName: {}
f:securityContext: {}
f:terminationGracePeriodSeconds: {}
manager: kubectl-create
operation: Update
time: "2021-04-12T10:18:47Z"
- apiVersion: batch/v1
fieldsType: FieldsV1
fieldsV1:
f:status:
f:completionTime: {}
f:conditions:
.: {}
k:{"type":"Complete"}:
.: {}
f:lastProbeTime: {}
f:lastTransitionTime: {}
f:status: {}
f:type: {}
f:startTime: {}
f:succeeded: {}
manager: kube-controller-manager
operation: Update
time: "2021-04-12T10:18:54Z"
name: sleepy
...
"