Create-llama is a user-friendly command-line tool designed to simplify the process of building full-stack applications using LlamaIndex for data loading, indexing, and interaction with language models like GPT-4. By executing a simple command, users can generate an app tailored to their needs, requiring only an OpenAI API key and some basic configuration decisions. Users can choose between Next.js, Express, or Python FastAPI for the backend, each offering different deployment options and file compatibility. The application supports a variety of file types for data ingestion, with the Python backend allowing for the most extensive range. Once deployed, the app can be customized extensively, including the option to switch from the default GPT-3.5-Turbo to GPT-4 or other language models, thanks to LlamaIndex's broad integrations.