Semantic Kernel is a software development kit (SDK) that integrates with large language models (LLMs) such as OpenAI, Azure OpenAI, and Hugging Face. It allows developers to interact with AI by defining chainable plugins, achieving AI integration within a few lines of code. Its key feature lies in the automatic orchestration of AI plugins, enabling users to generate plans for achieving specific goals using LLMs, which Semantic Kernel then executes.