CSS2 and CSS3 are both versions of the Cascading Style Sheets (CSS) language, but there are some key differences between the two.

CSS2 was released in 1998 and is considered to be a stable and mature version of the language. It includes features such as support for media types, cascading and inheritance, and selectors.

CSS3, on the other hand, is the latest version of the language and was first introduced in 1999. It includes new features such as animations, transitions, and new selectors. It also includes support for responsive design and new layout modules such as Flexbox and Grid. CSS3 also allows for better accessibility and more control over typography.

Additionally, CSS3 is not a singular monolithic release, it is a series of individual modules that are updated and released as they reach a certain level of maturity.

In summary, CSS3 includes new features and capabilities that were not present in CSS2, making it more powerful and versatile for web design and development.