Magento stores the additional information in table ‘sales_flat_quote_item_option’
1. info_buyRequest: For each item, this information is stored in a serialized array format. In this the entire form fields when adding product to a cart are stored in this. So product qty, custom options, configurable options etc are all stored in this.
2. Custom Options: The custom option id’s and value are stored in this table.
code: options_ids value: 1,2,3 (the options ids)
code: option_1 value: The value of option
code: option_2 value: The value of option
code: option_3 value: The value of option
3. Configurable Product:
code: attributes value: serialized array with all values selected