The central Server which stores the client and test hirarchy. This system should be placed on secure location in your intranet.
An Instance represents a monitored TYPO3-Installation. It is represented by an Instance Record on the Caretaker Server. You have to fill in the url and the hostname of the instance.
Instancegroups are usefull to group the monitored TYPO3-Installations to allow a better Overview.
Tests are the also created as TYPO3 Records. You first select the Type of Test you want to execute (Depends on the installed TestServices) and the desired Test-Execution-Interval. After a reload you will see a form with the configuration for your selected testtype.
Like Instances Tests can also be grouped and reused. For instance you can define a testgroup which will be assigned to TYPO3-4.1 installations.