In a differential game, the evolution of a system
is governed by an ODE of the form
$/dot x(t) = f( x(t), u_1(t), u_2(t) )$, $ t/ in [0,T] $
where $u_1$, $u_2$ are the controls implemented by the two players.
Each player seeks to maximize his own payoff. For example, this
may consist of a terminal payoff minus the integral of a running cost.

Various concepts of solutions will be reviewed.
These yield different models, depending on the information
available to the players and their ability to cooperate.

In some cases, solutions can be studied by looking at
systems of PDEs describing the value functions. 
Recent results on the well-posedness (or ill-posedness)
of these PDEs will be discussed, together with
the stability of iteration schemes based on the "best reply map".