Think of lists as the reference section of your model - they are literally lists of related items ("members" or "list items") that you will refer to as you build out the other parts of your model. For example, you might have a list of positions in the organization, or a list of product names, or a list of geographic regions. Lists should be quite stable over time. It's not that they would never change, but they are not changing based on calculations or assumptions.
A module is the part of your model where the work gets done, such as entering actual financial performance data, making calculations, or using assumptions to see projected results for various scenarios. A line item contains data or a formula, so if you had a module that calculated profitatability, you would probably have line items for each component of revenue (data, e.g, actuals or budget) and each component of cost (data, e.g. actuals or budget), with another line item for net profit (a formula).
The modules in your model refer to your lists to give your data the right context. They are referred to as the dimensions you are using in the module.