The Agora Extensions Marketplace is a platform that allows developers to add versatility, enhance user experience, or increase monetization to their video call apps by integrating extensions from various providers. The Synervoz Voice FX extension can be easily integrated into an Agora video calling application using the Agora console and Android Studio. The extension provides voice FX filters such as noise cancellation and voice changers, and can be accessed through unified billing directly from the console. To integrate the extension, developers need to enable it in their Agora console, download the SDK, and add the necessary code to their application. The integration process is straightforward and requires minimal configuration, making it easy for developers to enhance their applications with advanced voice FX capabilities.