When Victorian houses were built, cars were not yet invented, so the mode of transportation was horse and buggy. A carriage house would be built behind the house. It usually consisted of a lower floor, which held the carriages and tack, and sometimes the horses, and an upper floor where the person (or family) lived who cared for everything. That tenant might also be the driver. Depending on the wealth of the home owner, there might also be a barn for the horses and staff to care of them.
With the invention of the horseless carriage, these carriage houses were remodeled as garages with chauffeurs living above them. Changes over the years have seen them also turned into guest quarters or rented out to help pay the mortgage on the house. Also, many of the old Victorians have become bed and breakfast inns or straight hotels. Another use for them is historical museums. Carriage houses made into garages with the character left intact are still as beautiful as ever.
Because the Victorian houses belonged to people of wealth, they usually sat on larger lots. The carriage house was always located to the back of the property to keep the smell and noise of the animals and carriages away from the main house. Some homes had a porte cochere, which was like a narrow carport attached to the house, where the carriage would be parked and waiting for the passenger to enter the carriage. Today's cars won't fit under many of these porte cocheres unless they are widened.
Looking back, things weren't quite as easy as they are now. Many of today's homes have all of the conveniences anyone could want. So people looking for Victorian houses that have been kept true to the period or they wish to historically restore need to keep a few things in mind. First, they are going to get a lot of exercise both inside and outside. Second, they need to pare down their wardrobes or wear a lot of clothes that are folded. Third, the distance of that garage from the house seems even farther away when carrying things from the car to the house in cold weather.