VU (a.k.a. Venice Unleashed) is a modding and improvement framework for Battlefield 3. It offers a variety of features, such as the ability to host private dedicated servers, high frequency / tickrate servers, configurable suppression and color correction (ie. you can disable the blue tint), and extensive modding capabilities. With it, you can join servers offering custom experiences (such as the BF3 Reality Mod) or create your own using the modding tools.