The Eloi are a bright, happy people, who speak a simple language and are mainly interested in playfulness. They often play with flowers and other amusing items. Physically, they are shorter than humans, and weaker. ("The Time Machine: An Invention")
Additionally, they have a form of telepathy. Weena was able to sense The Time Traveler's presence in her mind, and became aware of strong, clearly-imagined thoughts of his. ("The Time Machine: A Sequel")
In Other Continuities
The Time Machine (1960 film)
The Eloi in the 1960 movie adaption like dancing and playing in the sun. They also enjoy making constructions with flowers. They have an intense, but almost subconscious, fear of Morlocks and of the dark.
They are fed, clothed, and otherwise cared for by the Morlocks.
The Time machine (2002 film)
In the 2002 movie adaptation of The Time Machine, the Eloi are depicted as identical to modern humans with a hunter-gatherer lifestyle, and appear to be an ethnic amalgamation of brown skin indigenous races. The former movie version depicts the Eloi speaking modern-day English, a fact which contradicts the original novel and the logical timeline of language evolution. In the latter film version, the Eloi maintain the English language as merely an intellectual exercise, calling it "the stone language," as they know of it only from surviving stone inscriptions from our time.