i'm doing some exercises and trying to wrap my head around how to write yaml build.

    spec:
  containers:
  - image: nginx
    imagePullPolicy: IfNotPresent
    name: nginx
    resources: {}
    envFrom: 
    - configMapRef: 
        name: anotherone # the name of the config map
  dnsPolicy: ClusterFirst
  restartPolicy: Never
status: {}

VS

containers:
  - image: nginx
    imagePullPolicy: IfNotPresent
    name: nginx
    resources: {}
    env:
    - name: option # name of the env variable
      valueFrom:
        configMapKeyRef:
          name: options # name of config map
          key: var5 # name of the entity in config map

So my problem here is: When do i use '-' symbol when i make a build in kubernetes ? I do understand that if i apply '-' before a string it makes it an object inside a list, but i don't understand when i need to use a list in a build in kubernetes.