The cart link in the upper-right corner of the header gives a quick summary of the contents of the cart. The link can be configured to display the number of different products (or SKUs) in the cart, or the total quantity of all items. If the mini cart is enabled, you can click the link to display more detail.
Example storefront - cart link at the top of the page
Configure the cart link
On the Admin sidebar, got to Stores > Settings > Configuration.
In the left panel, expand Sales and choose Checkout.
Expand the My Cart Link section.
Set Display Cart Summary to one of the following settings:
Display item quantities This setting displays the total number of products in the cart, adding the quantities for each product. Display number of items in cart This setting displays the number of product items in the cart, regardless of quantity.
Click Save Config.