Giants are often depicted as humans of abnormal size, at times hundreds of feet tall, and unlike the monstrous and ugly Ogre, a Giant tended to be depicted as very much a normal human, albeit greatly magnified.
In some cultures (most notably the Norse) Giants were also seen as embodiments of nature itself and were seen as formidable opponents of the gods (perhaps a throwback to memories of the Titans, a similar race of gigantic beings that warred with the Olympian gods in antiquity).
Although not as hideous or dimwitted as Ogres, the Giant was seen as cruel and often cannibalistic, for they would lord over some distant domain and often horded treasure or other goods and would sometimes attack villages or travelers in their spare time. Also, unlike the almost universally evil Ogre, the Giant was seen as a being that could choose to be good or evil and a great many Giants aided humanity as well as opposed it.
Much like the Ogre, a female Giant was known as a Giantess and she was often depicted as strikingly beautiful. In most fairy tales and folklore the Giantess was almost universally peaceful and when malignant was more of a deciever or trickster than a brute, though exceptions existed.