#Introduction

Argo CD is a very popular open-source GitOps tool. To use Argo CD, you need to understand the following core concepts:

1. Application: A group of Kubernetes resources as defined by a manifest. This is a Custom Resource Definition (CRD). Application
2. ApplicationSet: A Kubernetes controller supporting the ApplicationSet CRD, enabling bulk generation of Applications from a single template. Think of it as an Application factory that creates instances based on parameters. ApplicationSet
3. Tool: Specifies the configuration management tool for Application sources (e.g., Kustomize, Helm). Tool
4. Sync: The process of reconciling an application's live state with its desired state (e.g., applying changes to Kubernetes clusters). Sync
5. Health: Indicates an application's operational status, including readiness and ability to serve requests. Health

#Summary of Differences Between Application and ApplicationSet

Attribute	Application	ApplicationSet
Definition	Single application deployment	Template for generating multiple Application instances.
Configuration	Static YAML definitions	Dynamic parameter-driven template generation
Deployment	Single application	Multiple similar applications
Use Cases	Simple single-environment deployments	Complex multi-environment/cluster deployments requiring parameterized instances
Core Concepts	Git Repo, target cluster, deployment strategies	Generators, templates, parameters, placeholders
Role in Argo CD.	Fundamental deployment unit	Advanced bulk management layer

#Argo CD Sync Statuses

Sync Status	Description
Synced	Application's live state fully matches desired state.
OutOfSync	Live state diverges from desired state; synchronization required.
Syncing	Active synchronization in progress; live state converging to desired state.

#References

• Argo CD Official Documentation