The Payment Card Industry Data Security Standard (PCI DSS) is an information security standard for organizations that handle credit card and debit card information. Defined by the Payment Card Industry Security Standards Council, the standard was created to increase controls around credit card data to reduce credit card fraud via its exposure.
If you want to sell online and accept payments from Visa, MasterCard, American Express or Discover credit cards, your software and hosting needs to be PCI compliant.
Shopify meets all 6 categories of PCI standards. This compliance extends to all online stores powered by Shopify.