Indesign CS3 is desktop publishing (DTP) software that allows users to combine text, images, and illustrations into a single document. It provides tools for laying out pages, including options for single or double page views. Common tools include selection, text, and shape tools for working with frames. Panels can be customized and positioned on the screen. Basic functions covered include importing and placing images, formatting text styles for consistency, creating books from multiple documents, and exporting to PDF.