Earlier quoted context omitted.
You don't work in marketing/advertising. Companies need to segment populations of consumers with similar characteristics to effectively advertise, tailor products, and sell to them. One of the most common demographic dividers is age. Different "generations" are grouped together because the members of their population exhibit similar income and expenditure patterns on average.
Generations has been a concept long before marketing. I do wonder about who draws the line for where a generation begins/ends, but the concept is pretty clear: you are one generation, your children another, your parents another, your grandparents another. Hence the base word "generate".
Philosophers, novelists, sociologists, anthropologists, and economists used to define, study, and critique generational divides before advertising became such a pervasive part of the modern economy