Add "Key Concepts" documentation

This adds a new page that gives an overview of the different concepts in
Minder. It starts adding the items that were recently implemented and
are yet to be documented

Signed-off-by: Juan Antonio Osorio <[email protected]>

docs/docs/understand/key_concepts.md

@@ -0,0 +1,87 @@
+---
+title: Key Concepts
+sidebar_position: 05
+---
+# Key Concepts
+
+## Providers
+
+Providers are Minder’s integration points with external systems. These enable Minder to monitor and
+secure supply chain components by fetching data, notifying Minder of changes, and mapping external
+systems to Minder’s internal ontology.
+
+Examples:
+
+* GitHub and GitLab: Track repositories, pull requests, and CI/CD pipelines.
+
+* Docker Hub: Monitor container images and their metadata.
+
+Providers communicate with Minder through APIs, webhook events, and scheduled updates. This ensures
+continuous monitoring and up-to-date information about the entities they manage.
+
+## Entities and Checkpoints
+
+Entities are representations of key components in the supply chain, such as repositories, pull requests, or artifacts.
+They allow Minder to monitor and evaluate security practices over time.
+
+**Checkpoints**:
+
+Checkpoints are points in time that capture the state of an entity. These snapshots enable:
+
+* Auditability: Tracking changes and compliance over time.
+
+* Granular Analysis: Evaluating an entity’s state at specific moments, such as a commit hash or artifact digest.
+
+**Entity Lifecycle**:
+
+1. *Registration*: An entity is registered through its provider.
+
+2. *Evaluation*: Minder evaluates the entity against defined policies.
+
+3. *Action*: Issues identified during evaluation are either remediated or alerted.
+
+## Policies, Rules, and Profiles
+
+**Rules**:
+
+Rules define individual checks for specific aspects of an entity, such as ensuring secret scanning
+is enabled or that artifacts are signed.
+
+**Profiles**:
+
+Profiles are collections of rules tailored to a specific purpose or entity type.
+
+## Origination
+
+Origination describes one type of relationships between entities. For instance:
+
+* A pull request originates from a repository.
+
+This concept ensures that Minder maintains lifecycle consistency by:
+
+* Automatically creating derived entities (e.g., pull requests) based on originating ones.
+
+* Cleaning up dependent entities when the originating entity is removed.
+
+Example Relationships:
+
+    Repository -> Pull Request
+
+    Repository -> Release
+
+## Data Sources
+
+Data sources complement providers by fetching additional contextual information from
+third-party APIs. While providers manage entities, data sources provide an enhanced view
+of the entity. A common example is evaluating dependencies of an entity for security risks.
+
+Example Integration:
+
+A data source might query the Open Source Vulnerabilities (OSV) database to check
+for known vulnerabilities in dependencies listed in a repository’s manifest file.
+
+A data source might query an external service to check for the correctness and availability
+of release assets.
+
+These differ from Providers in the sense that they do not manage entities but provide
+additional context for evaluation.