By adding the "Dynamic checkout button" you will allow your customers to use the buttons for a quick product purchasing process. They can don't have to go through the cart but complete the transaction through the checkout method displayed via the dynamic checkout button. The checkout button changes dynamically to reflect the accelerated checkout method as per your customer's preference. 

The dynamic checkout button is displayed close to the "Add to cart" button. It's usable for purchasing products with single variants only. For example, a customer can buy two white vases but not one white and another blue vase. 

The third-party accelerated checkout methods available for implementation are:

• Shop Pay (Shopify)
• Amazon Pay
• Google Pay
• Apple Pay
• PayPal 
• Venmo