This can be implemented in many ways, but the goal is to orient the user and not make them wonder where they’re at or that the process will take a long time.

The convention here is the progress bar at the top of each checkout page, indicating where they are in the progress.

Accordion-style, single page checkouts are increasing in popularity because it allows for all the steps to be on one page (no extra page load times) and allows the user to see where they are in the process and to go back and edit the information if needed.