Unity is a platform made for 3D/2D games. It contains drag-and-drop functionality and is mainly complied in C++ (during runtime) and C# (for the Unity API).
It was made on June 8th, 2005. The most recent stable release as of June 15, 2018 is version 2018.1.2, which was released on May 25th, 2018. It supports 27 different platforms. It is able to run on Xbox and Windows (Direct3D (D3D) mode), OpenGL on Linux, MacOS and windows, OpenGL ES on android and iOS, and WebGL on web browsers.
Unity is still supported by its makers (as seen by the relatively recent update).
Flash has been deprecated and is being phased out as we speak.