Magento 2: Where is cart data saved?

Magento2, save cart details at Quote tables.

• For Cart general details use quote table .
• Carts item details at quote_item.
• Cart items option details at quote_item_option

Additional:

• Checkout Addressed details at quote_address.
• Checkout payment details at quote_payment.

Magento2 use Quote module Magento_Quote (vendor/magento/module-quote) for save all Cart general,items detail,address details etc.

And Mage_Checkout module's Session Cart model make relation between user,session with Cart details