# Internal Developer Platforms
All Internal Developer Platforms notes →1 — Introduction to Backstage
Introduces Backstage's architecture, core concepts, and plugin ecosystem as the most widely adopted open-source IDP foundation.
2 — Backstage Software Catalog
How Backstage implements the software catalog concepts from Part V: entity descriptors, catalog-info.yaml, and the catalog processing pipeline.
3 — Backstage Scaffolder
Backstage's Scaffolder plugin as the software-template execution engine: how a template becomes a running service.
4 — Backstage TechDocs
TechDocs as Backstage's docs-as-code layer: how documentation stays attached to its owning entity in the catalog.
5 — Backstage Plugins
Surveys the Backstage plugin ecosystem, Kubernetes, GitHub, Argo CD, Grafana, PagerDuty, Jenkins, and where a custom plugin becomes necessary.
6 — Extending Backstage
Extending Backstage beyond off-the-shelf plugins: custom plugin development, component overrides, authentication providers, and branding.