Midjourney is a generative AI platform that uses an LLM to create images from text descriptions. To get started, users need to sign up for Discord, select a paid or free plan, and start typing `/imagine` followed by their prompt. The LLM analyzes the prompt, creates a latent vector, and then converts it into an image using a diffusion model. Users can refine their output by adding parameters such as aspect ratio, style, and permutations to their prompts. Midjourney also offers advanced techniques like `--weird` parameter for generating unique outcomes and `niji 5` model for more sophisticated images. By understanding how to use these features and tweak parameters, users can generate majestic images exactly how they want.