Please refer to our Pricing page for an explanation of credits. An excerpt:
Credits are like tokens or coins. Each paid account comes with a predetermined number of credits that auto-renews every month. They are consumed every time certain actions exclusive to paid users take place, such as starting sessions and triggering exports.
Billing of the Geometry Backend API usage is based on sessions. There are two types of sessions that we bill for differently:
Embedded sessions (sessions created using a ticket for embedding)
Backend sessions (sessions created using a ticket for backend access)
Use case: Applications that access the Geometry Backend API from a backend application (not from a web browser), like E-Commerce or ERP systems. This might include batch processing.
1 credit is charged for each export request triggered
1 credit is charged for up to 10 computation requests triggered
Please note that desktop client applications make use of backend sessions as well.