Durkheim views society as the interrelationship of all its various parts (government, religions, the economy, & family). Through its various interactions, people create "ties" to others in society, these ties being the foundational "basis" of society. Societies exist under various levels of "cohesion" ("similarly & likeness"), that is, the extent to which they have "shared social sentiments," common beliefs, opinions, & feelings about the need for things like lawfulness, equal economic & educational opportunity, voting rights, etc. These common sentiments are what cause people in the society to feel obliged to respect the law, pay taxes, serve on juries, join the military, etc. Durkheim calls this concept "social solidarity," or the glue which holds society together.
However, as populations grow, their membership tends to become increasingly less similar, more diverse & "specialized in labor." This occurs as individuals work at "impersonal [selfish] companies" doing evermore efficient but mundane & unfulfilling jobs. This "specialized division of labor causes less self-reliance of people, and more dependence on govenment & society for the means of survival.