IM (instant messaging) is a feature that allows users to communicate with each other in real-time using text-based messages. The IM feature can be accessed through the Connexium client by 3CX, which is available for desktop, web, and mobile devices. 

It can also facilitate internal communication and collaboration within a company, as it allows employees to communicate instantly and share information and documents securely and privately.

The IM feature is a useful tool for businesses that want to improve communication and collaboration among their employees.