That’s how we call the configuration of a specific "Update type" (described below). By configuring the update behavior, we specify Drop Guard’s behavior in case of a detected update. You will adjust the branch for each update type, the process for failed patch and configure settings like testing behavior and git tags.
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. There are update types setting options in Drop Guard which are not related to security risks. For example, you may have "Normal" or "Unsupported" updates for your projects as well. Those, as well as security-related risk levels, are called the "Update types" in Drop Guard.
Tasks are the update jobs created by Drop Guard to process a single update, according to 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 got detected.