Semantic Kernel is Microsoft's open-source AI application framework that makes it easy to build AI agents and integrate LLMs into existing .NET, Python, and Java applications. It provides abstractions for prompt management, memory, planning, and tool use that enable developers to compose sophisticated AI workflows and agents on top of any AI model. Enterprise developers building AI-powered business applications on Microsoft's stack use Semantic Kernel as the recommended framework for adding LLM capabilities to enterprise software while maintaining the architecture patterns and development practices that enterprise software requires.