This chapter plays the role of an introduction to the subject of membranology. 
Here, we have gathered information and definitions regarding biological 
membranes that will subsequently become necessary. The principal purpose is to 
convince the reader that the available information on various origins is 
sufficient to reach the fully reasonable conclusion that the membranes can be 
viewed as two-dimensional surfaces in the three-dimensional Euclidean space and 
that the fundamental role in the shape of the membranes is played by the bending 
energy. The latter, in turn, is directly related to the membrane’s curvatures. 
This chapter surveys a series of biological, physical and mechanical aspects 
that are fundamental as a foundation for our results. This chapter plays a 
supporting role for our further considerations. We have collected required 
notations and definitions related to biological membranes, which we will make 
use of later. For more information, the reader can see the cited literature.