The document discusses the three waves of 1-1 messaging software:
1) The first wave introduced buddy lists and proprietary messaging like AIM, but was limited to computers.
2) The second wave saw the rise of SMS texting and services like Skype, Blackberry, and Google messaging that aimed to provide more affordable messaging.
3) The current third wave has seen exponential growth of messaging apps on smartphones, with WhatsApp, Facebook Messenger, and others gaining billions of users and developing new capabilities like payments and customer support in apps. Marketers need to understand where customers are interacting through these messaging platforms.