What is the difference between Gynecology and Obstetrics?

A lot of people assume that OB-GYN is just one specialization but some doctors specialize in one more than the other. The OB is someone who is involved in the preconception, pregnancy, and all of the other processes that are available that are related to the delivery of the baby.
GYN is now known to be the specialization for all of the health issues that may involve women. For example, some ovarian issues will be under the specialization of the Gynecologist because men do not have ovaries and they will have different problems that will not be part of what the gynecologist has specialized in.