Short answers, pulled from the story.
A game engine is a software framework primarily designed for video game development. It provides reusable systems covering rendering, physics simulation, audio, scripting, animation, artificial intelligence, networking, and memory management, allowing developers to build games without writing those foundations from scratch.
The term game engine emerged in the mid-1990s, driven by the rise of 3D games and first-person shooters. Epic Games debuted its Unreal Engine in 1998, and id Software's Doom and Quake popularized the practice of licensing engine technology to other developers around the same period.
One notable early example is the smooth side-scrolling engine developed by Shigeru Miyamoto's team at Nintendo for the NES. Built for the racing game Excitebike in 1984, it was reused in Super Mario Bros. in 1985, allowing Mario to smoothly accelerate rather than move at a fixed speed.
Unity and Unreal Engine are currently the two most popular choices for game developers. Godot, a free and open-source engine, saw a significant rise in adoption following the 2023 Unity pricing controversy, which led many studios to seek engines with permissive licenses.
A single license for a high-end commercial game engine can range from ten thousand dollars to millions of dollars. The number of licensees for engines like Unreal Engine has reached several dozen companies, making engine licensing a significant auxiliary revenue stream for developers.
Game engines are used in visualization, training, medical simulation, and military applications. They are suited to these uses because they are optimized for consumer-grade hardware rather than high-performance computing, reducing costs for researchers and developers working outside the games industry.