The Garter and the Plot
Each of the three acts of Verdi's Falstaff begins with a scene at the Garter Inn. In the first, Sir John Falstaff, the grandiose but impecunious knight, hatches a plot to improve his finances by charming some well placed wives of Windsor. In the second, Falstaff receives assignations from his intended victims, who have hatched their own plots against him. In the third, he recovers from his humiliations, and eventually is tempted into a final encounter in Great Windsor Park.
Verdi and his librettist Boito managed admirably to recreate the Garter Inn of Shakespeare's The Merry Wives of Windsor. A Shakespeare play, however, is not transformed into an opera libretto easily. In the play, scenes change with a bewildering abruptness, as we rush back to the Inn as soon as the plot demands it, and then we rush elsewhere following the rush of the comedy. In opera, the stage business takes much longer, the gestures are much broader, and singing takes longer than speaking. Everything , therefore, is much more tightly organized and focused in the opera.
Verdi's opera is called Falstaff, rather than The Merry Wives of Windsor. Falstaff is the central character. For Shakespeare (and for Nicolai) Falstaff is only one, albeit important, character in a comedy. Incidently, Verdi and Boito also borrowed a few Falstaff bits from Henry IV, but in that work Falstaff's headquarters were at the Boar's Head Tavern, in Eastcheap.

The Bar Review
The Garter Inn in Windsor is one of those stereotyped rustic hostelries that trumpet the solid values of Olde Englande. For all that, it is a bit of a dive. In fact, this is the sort of place your mother warned you to stay away from, since that is where grubby low life like Pistol and Bardolfe hang out. Of course your mother also warned you to stay away from Pistol and Bardolfe because they hung out at dives like the Garter Inn.
As an Inn, the Garter is a hotel and restaurant, as well as a bar. Falstaff lives there in one of the guest rooms. He eats there; the first act opens with the remains of breakfast still on the table. However, this is not a five star hotel. Alcoholic beverages are the principal attraction. Even at breakfast, several bottles and a glass are on the table. In the second act, Falstaff drinks sherry, while in the great third act scene just outside, he uses hot wine to restore his spirits.

How does the Bar fit into the Opera
Verdi's Falstaff could not exist without the Garter Inn. In fact, it would not work with an anonymous inn. It needs its own personality. Of course it does not stand independently as, perhaps, does TheCafé Momus from Puccini's La Bohème; it is always subservient to Falstaff's character. Falstaff is down on his luck, but he is a knight, and the Garter is his castle. Just as the direction 'a room in Ford's house' creates an impression of Ford's status in society, so the direction 'a room in the Garter Inn' creates an impression of Falstaff's status.
Falstaff, both in Shakespeare and in Verdi, is a complex character. He is at the same time noble, vulgar, ludicrous, tawdry, and magnificent. The Garter Inn parallels Falstaff's character. Its grandeur impresses us, even as it makes us laugh