Housing comes in many shapes and sizes. Real estate listings can describe a dwelling's architecture in terms of roofline such as mansard, or with characteristics such as Queen Anne, which features a turret that distinguishes it from being simply Victorian. Descriptions also denote building style in terms of proximity to other structures. The term "detached" represents a common way to explain that a property stands alone.
TL;DR (Too Long; Didn't Read)
When a building is detached, it does not connect to any other building and instead stands alone. In some cases, a building can be semi-attached and share a single outside wall with another building.
Detached vs. Attached House
The real estate industry refers to single-family homes that sit on their own lot without sharing any walls with another home or building as detached residences. Attached housing, on the other hand, shares walls on both sides with another home. Americans have consistently preferred single-family home ownership over other types of housing, although such structures are more common in the suburbs than in most cities. Detached housing provides distance between neighbors, a greater sense of privacy and more floor space than attached housing.
A home can be semi-attached if it shares only one outside wall with another home. The two residences in a duplex are each semi-attached because they have a common wall on one side. Semi-detached homes generally give owners less living space than fully detached housing, and they may require a more diplomatic approach to neighbor relations. If you reside in a duplex, such a home viewed as one structure on a single lot can be referred to as a semi-detached building.
Another type of detached housing, the detached condo, combines a single-family detached home with the ownership format of a condominium. Detached condos can offer owners a more homey feel to condo life and give municipalities an attractive alternative to traditional, high-density housing developments. Like condominium owners, detached condo owners pay association dues. Unlike owners of single-family detached homes, they may not own the land their dwelling sits on, just the building.
The term "detached" also applies to garages associated with residences. Attached garages did not become common in homes until after World War II, so a house with a detached garage is usually an older residence. A detached garage sits apart from the house, often adjacent to an alley behind it. While you can't enter the garage directly from the house, these structures have advantages. They don't sap residential heat or pose a fume hazard.