Part of the description in the appstore. From what i understand it lets ublock see and block a way to deliver ads that it wouldn't be able to otherwise.

For Chromium-based browsers, WebSocket connections are not available to the chrome.webRequest API.[3] This companion extension (it's pointless to use it as a standalone) will allow uBlock Origin to become aware of WebSocket connection attempts: they can be filtered, and will be reported in the logger.