What are specifications that allow you to customize a field beyond choosing a data type?
You can choose the size of some kinds of fields or the format of
some kinds of fields or validation rules for some kinds of fields,
an input mask for some fields, a default value for fields a
maximum, whether a field is required or not, whether it is indexed
or not and whether it is a primary key or not, as well as many
other settings. These are generally all known as properties of a
field.