Microsoft released Insider Preview Build 15019 for PC to insiders in the fast ring. This release includes a big update for Xbox Gaming including built-in streaming, new Games section in settings, and a new mode called Game Mode that is supposed to help with game performance. Other improvements and additions are new emojis, improvements to OOBE, and the ability to resize a Hyper-V virtual machine. Microsoft Edge can now read aloud* your e-book files opened using Microsoft Edge.
Source: https://www.bleepingcomputer.com/news/microsoft/windows-insider-build-15019-brings-us-a-game-mode-for-increased-gaming-performance/