We suggest a rigorous formulation of the problem of classification of equilibrium configurations of wetting films on solid surfaces and in pores taking into account capillary and adhesion forces. As example, cylindrical films and drops of a van der Waals liquid on planar substrates are considered. Rewritten as a dynamic system, the Derjaguin equation for equilibrium interfaces is analyzed in detail without numeric calculation of interfacial profiles, providing a simple way for understanding the different wetting regimes. This method allows us to enrich the arsenal of well-known explicit solutions responsible for clarifying such physical problems as wetting and dewetting, capillary condensation and desorption, imbibition and drainage, droplet formation, and foaming on inhomogeneous substrates and in pores.