As indicated by Shirish in another reply, IBA stands for Instance Based Attribute.
Since Windchill 10.0, and the addition of other options for attributes, they are called Global attributes, see Help Center here.
The Help Center is also a good starting point to gather more information on such Attributes and how to create them, here for Windchill 12.1
The article CS357203 collects different resources on Types and Attributes and could be an interesting next step.