A Single Family Detached Home is the technical term amongst demographers, economists, social scientists and the like refer to what many people would simply think of as a "home" or "house". A Single Family Detached Home is a structure that houses a single household, and shares no structural connections with another dwelling. Thus, Single Family Detached Homes stand in contrast to apartments, duplexes and condominiums.
The definition of the SFDH is fairly simple, as far as denotation goes. It is the connotations that are more interesting. When the census or social scientists want to capture the reality that is SES, they can't just have a questionare, with a Likert Scale: "Are you an ignorant yahoo that causes problems for your community in every possible way?" So social scientists depend on a number of other questions to determine people's SES, and one of these is the presence of SFDH, especially if combined with ownership of said home. A community that has a high proportion of SFDH is thus associated with being a wealthy, stable community, both statistically, and by the casual onlooker admiring the traditional homes.
A few weeks ago, I wrote a writeup under suburb, in which I pointed out that "the traditional suburban experience", for better or for worse, has little to do with how people actually live in suburbs. It was this in mind, that while on a recent MAX trip through Beaverton and Hillsboro, that I noticed the preponderance of condominiums and apartment buildings. Beaverton and Hillsboro are both considered fairly wealthy suburbs, so they would seem to be full of Single Family Detached Homes, but they seemed to have almost as many apartment complexes as Portland proper. After I did some research on dataplace.org, I found out that each one of these wealthy suburbs actually had LESS of a percentage of SFDH than Portland did. As I did more research, I found that while Portland was in this (as with many other things) atypical, it was not wildly so. Most cities have a good amount of Single Family Detached Homes (usually between 20-50%), and most suburbs have a somewhat higher number (40-80%).
Suburban areas and small towns can seem to have a higher prevalence of Single Family Detached Homes than they actually do because of the simple reason that they have a larger footprint. For example, a small town might have 20 square blocks, 19 of which are SFDH, and the other of which is an apartment complex. The apartment complex may have one quarter of the cities housing units, but that might not be apparent.
The basic point behind all of this is that the connotations of the Single Family Detached Home---high income and suburban---are not as one sided as some people might think. The connotations might erode even further as condominiums and townhouses continue to gain in popularity.
Sources: dataplace.org , which is really really good for poking around on.