Stratification is always a hierarchy, a division of society. In this case, the separation according to the principle of social belonging. There are many social strata, or strata.
A stratum is a unit of division in stratification. Since the concept itself came from geology, a stratum is a layer, a layer, not only in the earth, but in society. All people, one way or another, are members of various social groups. They can be distinguished an infinite number, if we take as a basis various principles of division.
For example, strata can be distinguished depending on age, material wealth, and ownership of property. A professional musician, amateur musician, just a listener - there will also be some kind of layers. In different historical periods, in different states, such a division could play a significant role in the life of all people. So, in India there were castes, in Russia - estates, in a later period - classes. Belonging to a particular group could determine the whole life of a person, from birth to death. In the same India, the transition from one caste to another was impossible. With great difficulty and luck in Russia, one could "climb" the social ladder. But to grow from a prosperous peasantry into a merchant class, the class of the petty bourgeoisie became real only closer to the 20th century.
But even now, stratification plays a large role in the social life of almost all people. Despite the proclamation of democratic principles, universal equality, in fact, it turns out that communication, financial situation, and certain types of activity allow certain privileges to be obtained. And society in one way or another is divided into layers lined up in a hierarchy. In general terms, it looks like a division into elites and masses. Those. At the bottom of the social ladder are, for example, ordinary workers, above are officials who can influence them, even higher are the ruling elite of the city, region, country, etc.
The division into layers can be carried out "horizontally", for example, by occupation. So, a famous musician and a famous athlete can stand on the same step of the "vertical" hierarchy, but at the same time they naturally belong to different social groups.
