CodeAssist is an AI-powered IntelliJ IDE plugin that provides natural language interface to generate, change, complete code and answer programming-related questions. It can work with popular programming languages and requires an internet connection. It offers a chatbot/copilot program that can generate code and provide answers to programming-related questions. Users can install it through the Intellij IDEA Marketplace and use it for free. However, there is a paid version available with more advanced features, such as GPT-4 long-term memory.