Setting up your online checkout
You can use the secure Shopify checkout to accept orders and take payments wherever you sell online. After a customer adds products to a cart, they use your checkout to enter their shipping information and payment details before placing an order.
When a customer reaches the payment method page of the checkout, their cart is checked against your store's inventory levels. If the inventory is available, then it is held for the customer while they complete the payment. If the inventory has become unavailable, then an error message appears. If a payment fails, then the hold is released until the customer reaches the payment method page again.
You can view and change your checkout settings from the Checkout settings page in your Shopify admin.
If you sell using the Online Store sales channel, then you can also change the appearance and layout of the checkout pages by editing your theme.