The difference between TeamViewer and TeamViewer IoT are the capabilities of monitoring. Whereas TeamViewer is designed to connect to computers and devices that control machines, TeamViewer IoT is specially designed to monitor and can connect to the machines themselves (e.g. smart building devices) for maintenance or health monitoring.
TeamViewer IoT is also meant to be used on IoT devices such as headless Linux gateways that have restricted resources and are not able to run the TeamViewer full version.
For more information, see the website under https://www.teamviewer-iot.com.