Standard attribute groups are not complex. By default, each attribute in a standard attribute group returns one value (for example, Age is 32). When creating an attribute, use the Allow multiple values option to store multiple values. See Creating or Editing Attributes.
Complex attribute groups are like tables of data and may return multiple values. For example, the complex attribute group Phone Account might include the attributes Phone Number, Data Plan, and Minutes Remaining. If the customer's phone account has three phone lines associated with it, then the channel returns the phone number, data plan, and minutes remaining for each of those three lines.
Complex attribute groups and their attributes are especially useful in criteria.
Vantage CX has a limit of 25 complex attribute groups.