An ENB (Enhanced Natural Beauty) is, essentially, a complete replacement of the game's lighting and shaders, in addition to any weather or lighting mods you might have installed. Two different presets can change the aesthetic of a game drastically; you should choose wisely and find one suited to your weather mod and/or game aesthetic. Do you want fairytale fantasy? Real life? Dark Souls? There’s a preset for every visual persuasion.
Of course, there’s a catch. Most (popular) ENBs may set your FPS on fire. There are many performance ENB options, however, and shaders can be individually disabled in-game, but if you are playing on a potato we highly recommend skipping this step.
A lightweight option is ReShade, which isn't nearly as powerful, but we will cover it. There is also Community Shaders, another lightweight option.
You will need:
KiLoader for some newer ENBs only.
Most ENB presets will have installation instructions, and some will require extra steps so make sure you read every mod page, but we'll help you with the steps for the most basic ENBs.
Extract ONLY d3d11.dll and d3dcompiler_46e.dll to your game folder. Find these in the "WrapperVersion folder in the archive.
Manually download the preset, and extract to your game folder: it should enblocal.ini, enbseries.ini, and an enbseries folder. If there are more files or folders in the same directory as these, install them too.
Watch the video, it goes more in-depth.
This isn't an exhaustive list. Check this category on the Nexus. Make sure you are downloading presets for whatever weather and lighting mod you use, and read the pages for recommended .ini tweaks and mods required for the desired look.
Culminated ENB (or anything else by firemanaf)
If you want to customize a preset, here is a breakdown of the different settings.
If you don't want to use ENB, but you want something similar that doesn't hurt your performance nearly as much, you can use ReShade. It isn't nearly as powerful, but you can get nice results.
Download ReShade and install it to your game directory, and install a preset from Nexus. The video and Nexus pages will have instructions.
If you don't wish to use ENB, then Community Shaders is another option. It has many feature add-ons (listed in the mod page) too. ReShade can also work with Community Shaders provided that it is configured properly. Here , here and here are some example ReShade presets for community shaders. You can check out more of these over on nexus.