households vs housing units

Housing Units contains both occupied and vacant housing units.  Households should equal the number of occupied housing units.

This is somewhat related but the Census (as well as different government programs) have various ways to aggregate within the household. Here is a little tutorial.. The idea is that there is a "householder."  For the ACS that is, in most cases, the person who fills out the survey form.  The ACS form says:

"(Person 1 is the person living or staying here in whose name this house or apartment is owned, being bought,
or rented. If there is no such person, start with the name of any adult living or staying here."

Person 1 is the householder.

So there is the concept of an "address" The Census has a Master Address File  (MAF)
The Master Address File (MAF) is a Census Bureau file that contains an accurate, up to
date inventory of all known living quarters in the United States, Puerto Rico and associated
island areas. The MAF is used to support most of the census and surveys that the Census
Bureau conducts including the decennial census, the American Community Survey and
ongoing demographic surveys. The content of the MAF includes address information,
Census geographic location codes, as well as source and history data.

There are issues with "dwellings" especially for native American/tribal areas.  There may not be a street or postal address.  People may be living in mobile homes trailers etc. For the Census all these people are counted. The ACS only "counts" people in the MAF and group quarters (I may not have the exactly right so someone comment.)

For some uses (and some ACS tables) there is the concept of the Family

A family is a group of two people or more (one of whom is the householder) related by birth, marriage, or adoption and residing together; all such people (including related subfamily members) are considered as members of one family. Beginning with the 1980 Current Population Survey, unrelated subfamilies (referred to in the past as secondary families) are no longer included in the count of families, nor are the members of unrelated subfamilies included in the count of family members. The number of families is equal to the number of family households, however, the count of family members differs from the count of family household members because family household members include any non-relatives living in the household.

see www.prb.org/.../

This is somewhat related but the Census (as well as different government programs) have various ways to aggregate within the household. Here is a little tutorial.. The idea is that there is a "householder."  For the ACS that is, in most cases, the person who fills out the survey form.  The ACS form says:

"(Person 1 is the person living or staying here in whose name this house or apartment is owned, being bought,
or rented. If there is no such person, start with the name of any adult living or staying here."

Person 1 is the householder.

So there is the concept of an "address" The Census has a Master Address File  (MAF)
The Master Address File (MAF) is a Census Bureau file that contains an accurate, up to
date inventory of all known living quarters in the United States, Puerto Rico and associated
island areas. The MAF is used to support most of the census and surveys that the Census
Bureau conducts including the decennial census, the American Community Survey and
ongoing demographic surveys. The content of the MAF includes address information,
Census geographic location codes, as well as source and history data.

There are issues with "dwellings" especially for native American/tribal areas.  There may not be a street or postal address.  People may be living in mobile homes trailers etc. For the Census all these people are counted. The ACS only "counts" people in the MAF and group quarters (I may not have the exactly right so someone comment.)

For some uses (and some ACS tables) there is the concept of the Family

A family is a group of two people or more (one of whom is the householder) related by birth, marriage, or adoption and residing together; all such people (including related subfamily members) are considered as members of one family. Beginning with the 1980 Current Population Survey, unrelated subfamilies (referred to in the past as secondary families) are no longer included in the count of families, nor are the members of unrelated subfamilies included in the count of family members. The number of families is equal to the number of family households, however, the count of family members differs from the count of family household members because family household members include any non-relatives living in the household.

see www.prb.org/.../