In science and research, an attribute is a quality of an object (person, thing, etc.).
The values are ordered in a logical way and must be defined for each variable.
Bigger domains have non-dichotomous variables and the ones with a higher level of measurement.
In this case the attribute "age" is operationalized as a binary variable.
If more than two values are possible and they can be ordered, the attribute is represented by ordinal variable, such as "young", "middle age", and "old".