Dentalink is part of your Dentrix software and is a way that you and your team can communicate with instant messenger. It pulls up a little bubble in the lower right corner of your screen. I have a lot of offices that use it to call the doctor in for exams, let the front office team know that they are running late with a patient or let the financial coordinator know there is a treatment plan that needs a financial arrangement.
The difference between your YAPI system and Dentalink is that Dentalink is only an IM feature and YAPI shows all the patients that are checked in and what room they are in. YAPI is kinda like a patient flow chart where Dentalink is only IM.