Help understanding what "upgrade" and "migrate" do

Hello, I'm currently running appwrite with k8s (well, a dirty "hack" of converting each container to a deployment). And I have some trouble understand what "upgrade" do in this doc: https://appwrite.io/docs/advanced/self-hosting/production/updates

This will pull the docker-compose.yml for the selected version/tag and perform the upgrade steps. Once the setup completes, verify that you have the latest version of Appwrite.

Well, since k8s (or in my case I'm running a k3s instance) is running with containerd, I think this "upgrade" will fail.

apiVersion: apps/v1
kind: Deployment
metadata:
  name: appwrite
  namespace: appwrite
  annotations:
    keel.sh/policy: "glob:v*-1.8.x"
    keel.sh/trigger: poll
    keel.sh/pollSchedule: '@weekly'
spec:
  replicas: 1
  selector:
    matchLabels:
      app: appwrite
  template:
    metadata:
      labels:
        app: appwrite
      annotations:
        backup.velero.io/backup-volumes: appwrite-config,appwrite-uploads,appwrite-functions,appwrite-sites,appwrite-builds
    spec:
      imagePullSecrets:
      - name: pull-creds
      containers:
      - name: appwrite
        image: my.private.registry/username/appwrite:v1.1.0-1.8.x

Here is what my deployment file looks like. I'm manually build appwrite form 1.8.x branch, and have CI/CD pipeline to upgrade image (newly built with latest commit from 1.8.x branch). Things works fine so far WITHOUT upgrade or migrate commands. But I'm worry about potential issue in the future if just leave it like this.

so

1. what does "upgrade" command do? is it the same as pull new code from appwrite/appwrite->build-> deploy to docker container?
2. I perhaps can run "migrate" before appwrite run, or does it need to be run as the same time as appwrite (new version) running?

upgrade -> upgrade appwrite instances from an older version to new. example: 1.6.x > 1.7.x, etc.

migrate -> migrating the internal data structure for databases for addition of new features on existing services or addition of new services altogether. This is required so that when you upgrade, your data structure inside the underlying database is up to date with backend sources.