With objects/entities selected, the next step is to tell the App where to display them. This is configured through Maps.
There are two types of maps - Grid Map and Form Map.
Grid Map is like a table in Excel, which is best for displaying a lot of data. For instance, Product and Pricing for Commerce Cloud below is using a Grid Map to display all the Product records retrieved from Salesforce.
As the name suggests, Form Map is suited perfectly for any single record. Let's say you want an App that allows the user to pick a single Account and its related Contacts. From the section above, we know a Grid Map is needed for the Contacts because there can be multiple Contacts in an Account.
Account, however, will always have only one record by design. This is where Form Map comes into rescue. It can display the Account in a form layout that is more natural for the users to navigate.