It tells us about the Swedish king Gylfi, who diguises himself as the beggar Gangleri and visits Asgard in order to find out everything about aesir and their wisdom. Odinn appears in the guise of three kings, Har ('tall'), Jafnhar ('As tall') and Thridji ('the third') and greets Gylfi. The three kings (Odinn) answere Gylfi's questions about the history of the world from the beginning to the end, of what the world looks like and of life in Asgard (heaven).
When Snorri wrote Gylfaginning he used Voeluspa as a source. The classical 'magister - discipulus' form that Snorri uses is common in mediaeval books.
