While creating an invoice, there are two different ways to create an invoice: Standard & Template

Standard: it's a single invoice. The link will be expired once a customer will complete this payment. 

Template: It will generate a link, and you can share this link to your customer via any source (message/WhatsApp/email, copy/paste), and the same link will remain open to re-use anytime. (you can also control the expiration date while making the template

The payments done thru the Template mode will be tagged as API(Type).