The Cuban economy has slowly been liberalizing in recent years, giving individual Cubans more ways to generate their own income outside the centralized state economy. Cubans have actually been legally allowed to rent rooms to guests since 1997 under the Castro regime, so today there are thousands of such accommodations available throughout the country, easily identifiable by the display of distinctive blue roof symbol.
Casa particular is a broad term -- it can mean a simple room in someone's home or a series of apartments under skilled management ... with or without breakfast included. Baths may be private or shared. Your hosts may also offer to cook you dinner, wash your laundry, or provide other services for a fee.
Price is a big selling point for casas particulares: they can cost a fraction of what you would pay for a hotel room. Another benefit is the invaluable opportunity to live and dine with Cuban residents and learn a little about the "real" Cuba behind the headlines.
Visitors to Cuba can book casa particular rooms directly with owners or through any of several booking agencies, including: