Hi René, welcome to AS.org
I don't know of any tut that explains this:
The properties are used for manipulating clips or objects in general. If you want to use script to do that you need access to the parameters, and you do this with setting values to the oject's properties. Let's say you have made a copy of the symbol (=instance) and you have placed it on position 10,10 but want to have it moved to 100,20 when you press a button. You would need access to its properties _x and _y .
There again nearly everything you can program you can do manually by using gotoAndPlay() . Just use tweening in the above sample, and jump to the start of the tween when pressing a button.
If you select an instance you will see in the property inspector a field <instance name> or something similar. That is the field where you name your instance.