  Theoretical models for the solar dynamo range from simple low-dimensional
``toy models'' to complex 3D-MHD simulations. Here we mainly discuss
appproaches that are motivated and guided by solar (and stellar) observations.
We give a brief overview of the evolution of solar dynamo models since 1950s,
focussing upon the development of the Babcock-Leighton approach between its
introduction in the 1960s and its revival in the 1990s after being long
overshadowed by mean-field turbulent dynamo theory. We summarize observations
and simple theoretical deliberations that demonstrate the crucial role of the
surface fields in the dynamo process and and give quantitative analyses of the
generation and loss of toroidal flux in the convection zone as well as of the
production of poloidal field resulting from flux emergence at the surface.
Furthermore, we discuss possible nonlinearities in the dynamo process suggested
by observational results and present models for the long-term variability of
solar activity motivated by observations of magnetically active stars and the
inherent randomness of the dynamo process.
