Dear Bruno,
It appears that you imagine a certain similarity between Revit and AutoCAD.
I am sorry to say that they are very different animals.
Here are a couple of related discussions and explanations:
http://thebuildingcoder.typepad.com/blog/about-the-author.html#5.41
I would suggest that you take a look at getting started with the Revit API to understand the programming side of things:
http://thebuildingcoder.typepad.com/blog/about-the-author.html#2
However, before you even start thinking about programming anything in Revit, it is of extreme importance that you understand the product usage from a manual end user interface point of view.
In your case, understanding the family editor, its principles,basic functionality and usage would be of utmost importance.
The Building Coder does provide a whole bunch of discussions that are oriented around that topic, mainly from a programming point of view:
http://thebuildingcoder.typepad.com/blog/about-the-author.html#5.25
Probably an end user tutorial would be of much more use to you thatn looking at the programming side of things, though.
I hope this helps.
Best regards,
Jeremy