Gulliver's Travels is a satire presented in the first person point of view, as a journal kept during Lemuel Gulliver's various adventures throughout the known and unknown world. Travelogues were quite popular during Swift's time, and so his audience would be familiar with such a style. Because so much of the world remained unexplored by Europeans, Gulliver's reports of the lands (especially their locations) would not seem as obviously fictional as they seem today.
The most significant aspect of Swift's narrative technique is the use of Gulliver as an unreliable narrator. At first, his attention to detail and revelation of embarrassing events leads the reader to trust Gulliver. He is an educated man- a surgeon, in fact- and he approaches each new situation with almost clinical precision. Yet slowly, he begins to reveal himself as humanly fallible. He admits to lying about English history, in order to present his country as more favorable to the Brobdingnagian king. He also appears incredibly naive and a bit dense, as he cannot grasp any society different from that of England (until his last voyage). Essentially, we cannot trust Gulliver's opinions on these lands, which is Swift's intention. Through that questioning of Gulliver as the narrator, the satire of the text is evident.