The Unreal Engine is not a 3d modelling package, altough it includes tools to modify models. It is a piece of software that coordinates all the innerworkings of 3d visualization, audio, and input control to produce an interactive 3d experience. Or in other terms, it's the guts of a game & the tools used to modify the content from 3d packages to fit the needs of the game.
The Unreal Editor (UnrealEd) is a pure “What You See Is What You Get” content creation tool filling the void between 3D Studio Max and Maya, and shippable game content.
Unreal provides plug-ins for 3D Studio Max and Maya to bring models into the Unreal engine with mesh topology, mapping coordinates, smoothing groups, material names, skeleton structure, and skeletal animation data. Including fully integrated source control, so that artists and level designers can check out content packages, modify, and check in from within the editor.
...and that is how I saved the world.