The product and customer inputs lets the user pick a set of existing products and customer from the master data. The two inputs work in the same way except that they let the user pick data from different tables..
Product
The product filter allows the user to provide a set of products as inputs. The end-user can either select products from a list, or provide a filter that will be used to query the product master table.
Customer
The customer filter allows the user to provide a set of customers as inputs. The end-user can either select customers from a list, or provide a filter that will be used to query the customer master table.