Lots of Unity’s features and systems have been upgraded in Unity 5, including Physics, Audio, Animation, ShadersA program that runs on the GPU. More info
See in Glossary and more. While many areas are upgraded automatically when you open an older project, there are certain areas where you may need to manually adjust or refactor parts of your project.
These pages are a quick reference to most of the changes that you need to be aware of when upgrading a project from Unity 4 to Unity 5: