Unity is an entirely different engine, it’s entirely different to UE4, whatever you made in Unity is solely for Unity, whatever you make in UE4 is solely for UE4.
An engine is basically a framework which provides game developers (of all sorts, from gameplay programmers, artists, graphical programmers, to level and environment designers, FX artists, AI programmers, etc) a set of pre-developed tools that are used to accelerate the development of your game / project. Rather than writing the renderer for your potential game from scratch yourself, you instead use an engine like Unity, Unreal, Frostbite or CryEngine which has all the work done for you, and use the engine’s tools rather than your own. Different engines typically do different things well: Unity is well known for being easily accessible, making it the first choice for a lot of indie hobbyist developers just starting out designing and developing games, CryEngine is known for being the pioneer for all sorts of rendering techniques that eventually may or may not make it into the industry (SSAO IIRC, which is the standard post-process ambient occlusion technique that games use, was first introduced by Crysis which used CryEngine), and Unreal is currently known for being an excellent free engine that delivers triple-A quality and reliability, with a great studio behind the helm (Epic Games). Both Unreal and Unity are not solely for VR, just that VR is currently a thing that’s taking off so a lot of studios are riding the bandwagon. You can use Unity and Unreal, or any other engine for that matter, for anything you want that fits the engine’s criteria: game development, real-time films, architectural visualisation, anything.
When choosing what engine to use, it’s a very important choice as for the most part everything you do in one engine cannot be translated to any other: if you start off using Unity, most of your work cannot be moved over to Unreal. Unity has a bunch of tools for level desgn, but UE4 also has it’s own tools for level design through landscape actors, BSP geometry, static and skeletal mesh actors and spline mesh actors.