Publisher Summary Communities are composed of the species that occupy a site. Identification of patterns in community structure has been a major goal of ecological research. Ecologists have developed a variety of nontaxonomic approaches in describing community structure, which provides different types of information to meet different objectives. The diversity of approaches has hindered the comparison of communities that have been described in different terms. However, distinct geographic patterns can be seen in community structure, and some community types characterize particular habitat conditions. A number of factors determine community composition, distribution, and dynamics. This chapter focuses on approaches to describing community structure, and on biogeographic patterns and underlying factors, which contribute to community structure. Species diversity has two components: richness and evenness. Richness is the number of species in community, whereas evenness is a measure of relative abundances. These two components can be represented by rank–abundance curves and by diversity indices. The study briefly explains the approaches describing communities, patterns of community structure, and determinants of community structure.