The Three Broomsticks is one of the major attractions of Hogsmeade for the staff of Hogwarts, and the students on their infrequent Hogsmeade weekends. Located on the main street of Hogsmeade village, it is a warm and cheerful place, presided over by Madam Rosmerta, a warm, cheerful, and curvaceous witch.
We should note that many major revelations occur in the Three Broomsticks. The subsections below are intended to serve as spoiler warnings.
Harry's first visit to the Three Broomsticks is extremely alarming; it is here that he hears the story of how Sirius Black had betrayed his parents, and killed another wizard and a number of Muggles.
It is in this pub in Harry's fourth year that Harry is invited by Hagrid to come and see the dragons that will make up the First Task of the Triwizard Tournament; at the same time, we learn that Alastor Moody's magical eye can see through Harry's Invisibility Cloak. Later in the same year, Harry is offered information on beating the Second Task by Ludo Bagman, and Hermione tells off Rita Skeeter, an action that results in Rita writing a scurrilous story...