Apache ActiveMQ is an open-source message broker that facilitates communication between different applications by sending messages between them. It supports various messaging protocols, making it versatile for different programming languages and platforms. This allows developers to build scalable and reliable systems that can handle large volumes of messages efficiently. ActiveMQ is designed to be easy to use and integrate into existing applications. It provides features like message persistence, which ensures that messages are not lost even if the system crashes. Additionally, it supports both point-to-point and publish-subscribe messaging models, catering to various use cases in enterprise environments.