In this context, "2" is the major version number of the App.
Consider that where many users and organisations (contributors here included) often refer to an iPad model using an unofficial short form identifier (e.g., iPad2, iPad mini6 etc.), whereas Apple generally uses a full model name to identify devices (e.g., 2nd generation iPad, 6th generation iPad mini). When Apple use a shortened name, such as iPad or iPad mini, they refer to the current model (i.e., the 10th generation iPad, 6th generation iPad mini).
Hopefully this information will disambiguate any product descriptions that you encounter in Apple documentation or advertising materials.
Where, specifically, are you seeing a potentially ambiguous description?