Residence of Bilbo Baggins, and later Frodo Baggins, the heroes of The Hobbit and The Lord of the Rings, respectively. In The Hobbit, Bag End is a place of refuge and peace to which Bilbo returns as his adventures end. (The novel is subtitled ``There and Back Again''.) In The Lord of the Rings, it is the location of the final battle of the war of the Ring, to evict Saruman from the Shire.
The first few pages of The Hobbit give a complete description of this Hobbit hole, but an idea of the evoked setting is given by the first few paragraph of The Hobbit:
``In a hole in the ground there lived a hobbit. Not a nasty, dirty wet hole, filled with the ends of worms and an oozy smell, nor yet a a dry, sandy hole with nothing in it to sit down on or to eat : it was a hobbit-hole, and that means comfort.''
(J.R.R. Tolkien, The Hobbit)