Twilio Client for iOS is a popular library used by developers to build Voice over Internet Protocol (VoIP) applications. Installing it using CocoaPods simplifies the process of adding dependencies to an Xcode project. To get started, install CocoaPods and create a podfile with the TwilioSDK package. Then, run `pod install` to install the pods. The resulting workspace includes a new Pods project that contains library files, frameworks, and WAV files used by the Twilio Client library. However, adding two values to the plist file is still required to enable VoIP functionality in the background.