Data Type represents a semantic definition of a data element which has a defined classification structure. For example, in your banking application, there could be different types of Accounts grouped as follows. You define and manage Data Types from the Data Type module.
Data List represents a static/flat list of values applicable for a given field in your application. For example, list of Account Status could be as follows. You manage Data Lists from the Resources tab under the Navigator menu.
When you define an Action Input Parameter, it’s data source could point to either a Data Type or Data List. In both the cases, system makes use of information in the Data Type or Data List to calculate optimized permutations for test case generation.