Race refers to a way to group people together primarily based on physical appearance. Those physical traits, such as eye/hair color, size, skull shape, and other measurable physical attributes are inherited from their ancestors and are considered genetic traits.
The idea of race seems to mainly be a 19th and 20th century concept and is losing currency among sociologists, biologists, and others. What we think of as racial characteristics today may not be nearly as ancient and ingrained as is commonly believed, and racial characteristics can change over a relatively short period of time.
The increase in "mixed race" children and families is another factor in making race a less useful grouping, if it ever was one. Many sociologists believe that race has done little other than divide people and isn't something which fits into academic studies of humanity.
This previous question on the same topic contains some more in-depth discussion.