An Ogre is the generic name for hideous creatures, usually giant-sized, who scare humnas. The female version is an Ogress. Ogres to me are creatures like Shrek and Fiona, from the movie Shrek. That is what I think of when I envison an Ogre.
Obviously their appearance gives them a bad reputation, as does the fact that are supposed to feed on humans.
Nymphs are born of Gaia, also known as mother nature in the Greek pantheon. They are associaited with nature and are often found protecting natural habitats. Nymphs can also be seen around Pan, Hermes, Apollo, Atremis, Dionysius, as well as creatures such as Satyrs.
Nymphs are described as beautiful and sexually attractive. They love to dance and sing and they are, ahem, quite armourous too.
They live for a long time, it is said they do not die from old age, but usually die in other ways. That they can live for so long often gives the impression they are immortal, though they are not. They often bear a child to a God – whichever one they have mated with – and these children are immortal.