Twilio Client allows browsers and devices to receive and send voice calls. This API could be valuable to integrate softphones, web conferencing, and click-to-talk services in applications. The site shows a quickstart guide in PHP where users can make calls from a browser, receive calls in a browser, and make calls between two browsers. Some of the prerequisites include a browser that supports Twilio client, an account, a web server to test the sample code, and a Twilio helper library. The library can be found in a redirected link and the code can be downloaded in a zipfile.