This chapter will cover the basic concepts of air-sea interaction. It has three sections. After the introduction about the importance of the phenomenon, its two-way nature and the scales (time and space) on which it is important, there is a section on exchange of momentum, energy and mass between the atmosphere and the ocean. Part of this section addresses some of the aspects of modeling approaches used in a variety of problems which are connected to or influenced by air-sea interaction. Air-sea exchanges are strongly influenced by the structures of both media near the atmosphere-ocean interface, notably boundary layers that are present in both media. Therefore, we give a brief discussion of boundary layer structures and we examine in particular the role of the viscous sub-layer in the atmosphere. Then we present the most common approaches to the modeling of these exchanges. We start with some relatively simple concepts such as “Bulk” formulae and then present some more complex approaches. It is difficult to evaluate the quality of a particular model. We usually look into the effects of flux calculation and then, indirectly, we judge about the quality of a particular scheme or approach. Therefore, we present calculations of the sea surface temperature (SST) for the Mediterranean Sea obtained by a coupled model with particular modeling of fluxes. Comparing observed and calculated SST’s we offer some ideas about the quality of modeling in that case.