What are the different age groups and their names to be considered for a Marketing Research study?

1. Please let me know the the age groups with names (like teenagers, young adults, adults, etc) in young generation. They can be from age 10-40.
2. Do they differ by countries or they are same everywhere?
3. And for online shopping research, which age group would you suggest to study?

Thank you so much in advance for the help :)