Halfling is the common name used by humans for the Hobbit race in J.R.R. Tolkien's Middle Earth stories; most notably The Hobbit and The Lord of the Rings. Tolkien's Hobbits are generally rural farmers and not particularly adventurous.
Such races are the focus of the Halflings, Hobbits, Warrows & Weefolk anthology (ISBN 0446392812).
Halfling is one of the standard playable races in the D&D RPG settings, where it is specifically a different race than Gnomes. In the original version of D&D they were Hobbits by name, but threats of legal action forced a name change to the generic halfling.
Over the course of the three editions of AD&D and D&D 4th Edition, the race has further diverged from Tolkien's vision. With the Dark Sun game world portraying them as cannibalistic barbarians, and the core game portraying them as adventurous acrobats.