A configuration for the specific "Update type". By configuring the update behaviour we tell Drop Guard what to do in case an update of a particular kind is detected. Should it create a feature branch, figure out how to process failed patch, decide which branch to use for the update - those things are covered in the update behaviour configuration.
This is how we call the well-known "risk levels", although in a broader sense. Check the Drupal.org page on the risk levels for more details. You may wonder why we didn't use the "risk level" term - the answer is that there are a couple of update types in Drop Guard which are not related to security risks at all. For example, you may have "Normal" or "Unsupported" updates for your projects. Those, as well as security-related risk levels, are called the "Update types" in Drop Guard.
The update job created by Drop Guard to process a single or a group of related updates, depending on the configuration. For performing actual updates Drop Guard creates update tasks which can be processed manually (by executing them from the interface), or automatically as soon as the update is detected.