Lesson 1

What Is YAML?

Understand YAML structure and where developers use it.

YAML (YAML Ain't Markup Language) is a text format for structured data that prioritizes readability. Developers use it when humans edit configuration files by hand more often than machines stream bytes.

Three core structures

Mappings — key/value objects, written with indentation:
```
app:
  name: DevCove
```
Sequences — ordered lists, often with -:
```
features:
  - json
  - yaml
```
Scalars — strings, numbers, booleans, and nulls.

Indentation matters

Unlike JSON's braces, YAML uses whitespace to show nesting. A sibling key at the wrong indent level changes the entire tree—and parsers fail with line/column errors.

Comments

YAML supports # comments, which is one reason teams choose it for Kubernetes and CI files that need inline explanations.

Where you see YAML

Kubernetes manifests (Deployment, Service, ConfigMap)
GitHub Actions and GitLab CI workflows
Docker Compose files
Ansible playbooks and Helm values.yaml

YAML describes data shape. It does not execute commands by itself—tools like kubectl, Actions runners, or Compose interpret the files.

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