In Stata categorical or binary, indicator, dummy variables (used interchangably) are treated as factor variables. Examples of categorical are industry workers or members of a race which all contain several categories (ie. black, white, asian). In the case of indicator variables, there are only two categories denoted by 0 and 1, meant to represent a characteristic such as if respondent lives in south or if a car is foreign. Stata treats categorical variables as factor variables and in operations they are prefixed with an i, such as:
sysuse nlsw88, clear
summarize i.south
The results are shown for the southerners in the sample (1), the same result you would get with just summarize south. The baselevel is 0 and to show that, use allbaselevels:
summarize i.south, allbaselevels
To get statistics for the baselevel (ie, south = 0) use:
summarize ib1.south
Perhaps more interesting is to get statistics for all levels:
summarize ibn.south
