Humans are by far the most prolific race on the surface world and tend to be the most versatile. One wise scholar once pointed out that the only constant thing about humans is their diversity.
Humans as a race are not known for any special abilities like the other races, but they don't have any racial handicaps (like iron), either. Typically, all establishments in a city or other civilized area welcome humans, and while other races may treat humans with a degree of suspicion occasionally, this is just caution on their part, not racially-motivated behavior.
It has been said that to err is human, and dwarves, elves, and halflings might agree that humans often make blunders, but it has also been said that one learns from one's mistakes. Legend states that the human race was put on the earth as an experiment. The deities simply wanted to see what would happen if a race completely free to exercise its judgment but lacking the kind of wisdom that comes from a millennium-long lifespan or a closely-knit societal structure could survive and prosper. The experiment is still under way and the experimenters (deities) have to stir the mix every now and then.
Typical humans range in height from about five feet to six and a half feet and may weigh anywhere from 100 to 250 pounds. Hair and eye color can be any, as can skin tone. An average human lives from 70 to 90 years per lifetime, but members of many human religions experience several births. Although few humans are aware of it, their actions usually determine the state in which they will find themselves in the next life. Ultimately, it depends on a human's religion and the judgment of his or her deity, if any.
A human could come from a nomadic, amazon, barbarian, civilized, feudal, desert-dwelling, sea-faring, nature-worshipping, nihilistic, atheistic, or fatalistic society. It's all a matter of choice with humans, as are all human endeavors.