Hardy uses both third-person omniscient narration, which is when the narrator stands outside the text and explains what is going on to us, and first-person narration from characters within the text who are eyewitnesses to a particular scene. The omniscient narrative is what is known as "extradiegetic" (outside the text), while the subjective narrative from the point of view of a character within a scene is called "intradiegetic". Intradiegetic narration allows the author to withhold or slant information so that it is misrepresented or so that the reader doesn't know everything that is going on. For example, when Venn describes the Thomasin wedding as he experiences it, he misses certain aspects.
Hardy also uses narrative technique to emphasize his naturalism, especially the idea that humans are insignificant against the vast sweep, power, and history of the heath—a part of a larger natural world that is largely indifferent to or mocking of the fate of humanity. His narrator sets this tone by devoting the entire first chapter of the novel to the heath and its description. We get a history of the region and some description of human interventions, such as roads, but the narrator tells us that the heath is, overall, the "enemy" of civilization. By this, Hardy does not mean that it is malevolent to civilization but that it wears civilization down and outlasts it. People are lumped by the narrator with the sea and fields as transitory natural forms against the everlasting heath:
The sea changed, the fields changed, the rivers, the villages, and the people changed, yet Egdon [heath] remained.
It is not until the narrator has established humankind's insignificant place in the universe that we move to the second chapter, where the human world is introduced.