Theer's a lot of technical details I don't understand. What is "Messenger" and what is "message web interface" and what exactly is it that he desperately needs

Theer's a lot of technical details I don't understand. What is "Messenger" and what is "message web interface" and what exactly is it that he desperately needs to sync? Contacts? Aren't they already store on the phone when you sync against gmail? SMS? Aren't they already stored on the phone? The same with call history, right?