What is enb and reshade?

I see a lot of modders talk about ENB and reshade being the first step to graphic enhancement of games. What are they?

They basically enhance graphics, reflections, colors etc.

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This is what reshade looks like.

https://imgur.com/vQj8uh9

I see a lot of modders talk about ENB? I did not understand

They're just a fancy way of saying they modified the shaders on various assets, such as the ambient lighting (the thing that makes shadows work and defines the feel of the game), surface reflections (like on water), textures and others. ENB and Reshade are just two different styles of the same concept. If you don't know what a shader is in computer graphics, it's best to look it up.

ENB and Reshade modifies the shaders, lighting, textures, and many more, they also allow modifications for different mods, famous games including Fallout: NV, and Skyrim.

ENB is a tool that wraps an existing engine and injects additional graphical effects. For Bethesda games it can even provide a performance boost.