CMD J is a Chrome extension that uses AI technology to help improve the user's writing, coding, copywriting, and search capabilities. It provides access to unlimited AI-powered writing assistance, code explanations and answers to hard questions, post drafts for social media or blog posts, and human answers to Google searches. It is available in four pricing plans, ranging from free to Ultimate, with varying features and request limits. Users can access ChatGPT's features with a simple Cmd/Alt + J keyboard shortcut.