What is the difference from Generations X, Y, and Z?

It is a common trait for the youth of whatever newest generation to be careless and disrespectful to those older than them. It has always been a common trait for the current eldest generation to call the younger ones lazy and entitled.
Certain defining events of specific generations can help to develop their characters, most people associate this with the silent generation that was raised during the Great Depression, or the lost generation of World War I.
The only thing that will distinguish the generations of X Y and Z in a few decades will be the difference in technology between the three, and perhaps 9/11.

Gen X are the offspring of the Baby Boomers. Millennials are the offspring of Gen X. Gen Y was originally a marketing term used to identify the kids who were the anticipated consumers of goods aimed at children and adolescents, when Gen X was not old enough for many of them to have started raising families. In fact, many of those "Gen Y" consumers were actually younger Gen Xers. As the Gen X cohort matured past the stage where even the youngest of them were not interested in such products, "Gen Y" became disused, and then became associated with the Millennial generation. "Gen Z" is a place-holder designation for the offspring of Millennials, but because Zombie stories were popularized by Gen X, this designation will probably be supplanted with a different name, in the near future.

Each generation in turn comes to believe as they pass through adolescence that their parents' generation are the stupidest, yet most opinionated, people ever born. They also believe their own generation has EVERYthing figured out. When they become parents they first believe that their children's generation are all beautiful geniuses, and 14 years later they believe their children's generation are all self-centered idiots.

Every generation of grandparents goes though a similar change of perspective, first thinking their grandchildren are angels while everyone else's grandchildren are defective or evil - and 14 years later concluding that their grandchildren's entire age cohort will be the one to end humanity's existence on the planet. (The grandchildren's generation becomes sure that they are the saviors of humanity, ironically because they are convinced that their grandparents' generation only narrowly escaped going extinct with the dinosaurs, since they understand NOTHING about ANYTHING - beyond handing out candy.)

The author of this imagination only knows EVERYTHING.

Their knowledge of real U. S. history is less and less.