The AG2 framework, evolving from the AutoGen project, provides an open-source infrastructure for building complex AI applications by orchestrating multiple, conversing agents powered by Large Language Models (LLMs). Its core philosophy is "conversation as programming," where structured message exchanges between agents drive computation and task execution. The ConversableAgent class serves as the fundamental building block, enabling flexible configuration of agent behavior through parameters like system_message and human_input_mode, and supporting secure code execution via Docker. AG2 facilitates robust multi-agent orchestration through patterns like GroupChat, allowing for centralized or decentralized control and providing comprehensive tool integration, structured outputs, and Human-in-the-Loop (HITL) workflows. This positions AG2 as a powerful "Agent Operating System" for AI researchers, engineers, and development teams creating advanced LLM applications.