It is tough to please John (without tough-movement) John is tough to please (with tough-movement)
As far as I can tell, in tough-movement, the focus of the sentence - in this case, the object noun John - is promoted to subject position, triggered by a restricted class of words (including easy, impossible and difficult). A tough-construction is simply one in which the dummy syntactic subject (it) and the syntactic object (John) are co-ordinated in this way. This paper (http://www.rceal.cam.ac.uk/Working%20Papers/andersonsum.htm) has a more technical definition.
Tough-movement
It is tough to please John (without tough-movement)
John is tough to please (with tough-movement)
As far as I can tell, in tough-movement, the focus of the sentence - in this case, the object noun John - is promoted to subject position, triggered by a restricted class of words (including easy, impossible and difficult). A tough-construction is simply one in which the dummy syntactic subject (it) and the syntactic object (John) are co-ordinated in this way. This paper (http://www.rceal.cam.ac.uk/Working%20Papers/andersonsum.htm) has a more technical definition.
Hope this helps. :)