A DO can be a heart surgeon if she wants. A DO can be an OBGYN. They have a medical license. It's like the difference between a DMD and a DDS. Some schools give one degree, some give another.

As has been stated above, you have likely been treated by a DO without even knowing it.

The funny thing is that people would inherently trust an MD who got his degree from the Caribbean, but they suddenly don't trust a DO who got his degree from a respected medical school in the US.

DOs take all of the same classes that an MD does. They often do the same residencies. They are physicians. They are not "osteopaths". That's a European term for a chiropractor essentially. DOs learn some things about osteopathic manipulation. There's some philosophical differences in terms of diagnosing and treating a patient. But they still have all the training an MD receives.