Shop Pay Installments allows you to pay in full at checkout, or to split your purchase into 4 equal, interest-fee installment payments for orders totaling $50 or more. Payments are automatically charged every 2 weeks.
If you choose to pay using Installments, you will be responsible for managing your payment schedule with Shop Pay & Affirm, Shopify's provider for installment payments.
See Shop Pay Installments overview and About Shop Pay Installments for more details.