The difference between RO-Properties and TO-Properties are that TO properties refer to the properties as they exist in the Test Object saved in the test (i.e. in the object repository or as described in descriptive programming) and the RO-Properties refer to the RunTime object (i.e. the object as it appears in the Application Under Test (AUT)).
From this distinction a few things arise
1.Accessing a TO property doesn’t require the AUT to be open
2.Accessing an RO property requires the AUT to be open and the object to be uniquely described
3.You can set the value of a TO property but not that of an RO property