Python 3.3 is a version of the popular programming language Python, released in September 2012. It introduced several new features, including the yield from expression, which simplifies the process of working with generators. This version also improved the handling of Unicode and added a new dict implementation that enhances performance. Additionally, Python 3.3 included the venv module for creating lightweight virtual environments, making it easier for developers to manage dependencies. It also provided better error messages and improved the standard library, contributing to a more efficient and user-friendly programming experience.