Answer
An Application is a custom resource (CRD) that represents a deployed app in ArgoCD. It declares the source (Git repo, path, revision, or Helm chart), the destination (cluster and namespace), and the sync policy. ArgoCD uses it to fetch manifests, compare to the live state, and keep them in sync.
apiVersion: argoproj.io/v1alpha1
kind: Application
metadata:
name: guestbook
namespace: argocd
spec:
project: default
source:
repoURL: https://github.com/org/repo
path: guestbook
targetRevision: HEAD
destination:
server: https://kubernetes.default.svc
namespace: guestbookReal-world example Each microservice is represented by an Application CR pointing at its manifests path and target namespace.