> 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/concepts.md).

# Concepts

- [Inversion of Control](https://docs.radicalframework.com/concepts/ioc.md)
- [Third party DI containers](https://docs.radicalframework.com/concepts/ioc/third-party.md)
- [Entities](https://docs.radicalframework.com/concepts/entities.md)
- [Property System](https://docs.radicalframework.com/concepts/entities/property-system.md)
- [Messaging and Message Broker](https://docs.radicalframework.com/concepts/message-broker.md)
- [POCO messages](https://docs.radicalframework.com/concepts/message-broker/poco-messages.md)
- [Standalone message handlers](https://docs.radicalframework.com/concepts/message-broker/abstract-message-handler.md)
- [Observers](https://docs.radicalframework.com/concepts/observers.md)
- [PropertyObserver](https://docs.radicalframework.com/concepts/observers/property-observer.md)
- [MementoObserver](https://docs.radicalframework.com/concepts/observers/memento-observer.md)
- [BrokerObserver](https://docs.radicalframework.com/concepts/observers/broker-observer.md)