H.G. Wells was primarily a novelist of ideas. Most of his works, particularly those which feature science fiction, are clearly focused on exploring concepts which he thought worthy of investigation. In The Time Machine, two such ideas are extensively explored: the relatively new concept of time travel and the idea of a future dystopia on a dying earth.
The Time Traveller lectures his guests on the scientific basis for his machine, explaining that time is a fourth dimension which one can travel through, as one does through the other three. Although The Time Machine is not the first work of fiction to deal with time travel (indeed, it is not the first such work by Wells), it does break new ground in explaining and illustrating the concept in a realistic manner.
Wells wrote several works of Utopian socialism, and The Time Machine initially seems as though it may be one of them, though the Eloi are rather insipid and lazy to be ideal beings. The point is quickly established, however, that such a harmless people would inevitably become the prey of some more dynamic and forceful creature. Wells's vision of the future is an idea of what might happen if the upper classes become ever more idle and dissipated, while the working classes continue to be oppressed and resentful. It is therefore a warning as well as an exploration.