Unity is software for 3D game development

Extensive 2D and 3D games and graphics applications can be developed with the free software Unity Engine. The Unity Engine helps developers create their own games. Unity generates code for games and 3D applications and offers 3D textures, real-time shadow on mobile devices, improved memory management and performance optimisation of the graphical user interface. Target platforms are game consoles, mobile devices and browsers in addition to the PC.

Unity offers the possibility to integrate music, sounds and noises, and for model landscapes and trees and plants to emerge. The editor is offered for free in the basic version, it can be used to realise complex projects. 3D models, textures, sounds and animations can be created and imported according to one’s own wishes and ideas. Physical properties can be added and their behaviour customised in the editor.

Unity can be supplemented by self-written program scripts

The built-in mechanisms in Unity can be supplemented through self-written programs called scripts. Scripts are necessary for determining game play and logic. The scripting in Unity is based on Mono and offers the scripting language UnityScript which is comparable to JavaScript, C# and Boo.

You can find more information on Unity on Wikipedia: https://en.wikipedia.org/wiki/Unity_(game_engine)

and on the official Unity company website: http://unity3d.com/