In this book, we will develop an AI application using Python, LangChain and Streamlit to leverage the ChatGPT API. The emphasis is on learning by building, starting from a simple chat app development and progressing step-by-step to an app that utilizes Embedding. Once the AI app is developed in a local environment, we will also learn how to deploy it on the web. You don't need extensive cloud knowledge, and the deployment method incurs little to no running cost. So, let's take up the challenge of publishing the created app.