> For the complete documentation index, see [llms.txt](https://docs.radicalframework.com/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://docs.radicalframework.com/release-1/concepts.md).

# Concepts

- [Inversion of Control](https://docs.radicalframework.com/release-1/concepts/index.md)
- [Castle Windsor](https://docs.radicalframework.com/release-1/concepts/index/windsor.md)
- [Autofac](https://docs.radicalframework.com/release-1/concepts/index/autofac.md)
- [Unity (v2 & v3)](https://docs.radicalframework.com/release-1/concepts/index/unity.md)
- [Puzzle Container](https://docs.radicalframework.com/release-1/concepts/index/puzzle.md)
- [Entities](https://docs.radicalframework.com/release-1/concepts/entities.md)
- [Property System](https://docs.radicalframework.com/release-1/concepts/entities/property-system.md)
- [Messaging and Message Broker](https://docs.radicalframework.com/release-1/concepts/message-broker.md)
- [POCO messages](https://docs.radicalframework.com/release-1/concepts/message-broker/poco-messages.md)
- [Standalone message handlers](https://docs.radicalframework.com/release-1/concepts/message-broker/abstract-message-handler.md)
- [Observers](https://docs.radicalframework.com/release-1/concepts/index-1.md)
- [PropertyObserver](https://docs.radicalframework.com/release-1/concepts/index-1/property-observer.md)
- [MementoObserver](https://docs.radicalframework.com/release-1/concepts/index-1/memento-observer.md)
- [BrokerObserver](https://docs.radicalframework.com/release-1/concepts/index-1/broker-observer.md)