Streamlit is an open-source Python library for creating web applications for data science and machine learning projects. It allows developers to create interactive and customizable dashboards with minimal coding. Streamlit is highly favored for its simplicity, as it enables rapid prototyping and deployment of machine learning models. With features like automatic UI updates and integration with popular data science libraries like Pandas, Matplotlib, and TensorFlow, Streamlit is an ideal choice for showcasing data insights and model results in an interactive format.