The Between operator defines a value range for a particular condition. It is used to select those contacts for which the relevant attribute has a value that falls within the range identified by the minimum and maximum condition input fields.
Setting the Date of birth condition to Between with 01/01/1980 and 31/12/1989 as the input field values, selects all contacts born in the 1980s.
Setting the Number of children condition to Between, with 1 and 3 as the input field values, selects all contacts with 1, 2 or 3 children.
See Input field types for more about each input field.