Based on the selected inventory model strategy stock transfers might be created from a stock location (i.e. secondary) from another (i.e. primary).
You can optionally define a custom alphanumeric (not case-sensitive) code for your stock locations, provided that it's unique across the environment (it can contain underscore and hyphens, spaces are not allowed , the maximum length is 25 characters).
Check the related ER diagram and explore the flowchart that illustrates how the stock location resource relates to the other API entities.
Check the related guide to learn more about the available inventory model strategies, how they work, and how stock locations are involved in the process.