Skype is a very popular Internet-based calling service that is available as a desktop and mobile application. Users can make free voice and video calls to other Skype users. They can also send free instant messages to other users.
Google Hangouts allows users to make free calls to other users. They can also send messages through the service. Users do not have to sign up for any additional accounts if they already have a Google account.
KakaoTalk is both a calling and a messaging application. Users can send and receive free calls and messages to and from other KakaoTalk users. It also has customizable themes, group chat features and animated emoticons.
WhatsApp is a widely used messaging application that lets users connect with an existing mobile number and send messages via a mobile Internet or Wi-Fi connection. It works in multiple mobile operating systems, so users can message people who use other kinds of phones.
Facebook Messenger uses Facebook's chat and messaging system to send and receive new messages. Users can send free text, photo, image and voice messages to any of their Facebook friends.Learn more about Mobile