"Another class of interesting models that typically cannot be solved analytically are
stochastic dynamic models of rational, forward-looking economic behavior. Dynamic
economic models typically give rise to functional equations in which the unknown is
not simply a vector in Euclidean space, but rather an entire function dened on a
continuum of points. For example, the Bellman and Euler equations that describe
dynamic optima are functional equations, as often are the conditions that characterize
rational expectations and arbitrage pricing market equilibria. Except in a very limited
number of special cases, these functional equations lack a known closed-form solution,
even though the solution can be shown theoretically to exist and to be unique."
What does "solved analytically" and "closed-form solution" means?