Q. Which product types exist in Magento? - Magento has 6 standard product types, including: Simple product, grouped product, configurable product, virtual product, bundle product and downloadable product.
Q. What are total models responsible for in Magento?
Quote, invoice, creditmemo
– grand total
dispatches event “sales_quote_address_discount_item” in collect method of Mage_Sales_Model_Quote_Address_Total_*
getCollectors() – Get total models array ordered for right *calculation logic*
getRetrievers() – Get total models array ordered for right *display sequence*