I think you meant the types of women's health nurses?
Mother/baby and post partum are basically the same thing. They take care of moms and babies from sometime after delivery until they go home.
Some of these mother/baby and post partum units utilize a nursery also, which would have some nursery nurses. And trust me, they do far more that rock babies.
L&D is where the mom actually delivers. There's also what we call at our hospital "Special Care," which is the equivalent of a high risk L&D. We also have our own mini OR (I believe it has 3 or 4 rooms) for sections.
Then there are antepartum and gyn nurses. This unit is lumped together at my hospital. Antepartum is before delivery, moms to be that are hospitalized for one reason or another. And gyn nurses take care of gynecological surgery patients.
And OB/GYN nurse is usually just a generic umbrella term, it can usually mean anyone of the types I've mentioned.
On each of these units, except for L&D, I've seen LPN's.
Hope I didn't forget any of the disciplines of hospital OB nurses, and I hope, after writing this mini novel here, that it was the info you wanted!