Case Number and Case ID are two different identifiers on a Case record in Zoho CRM, and it's easy to mix them up since they both look like reference numbers.
Case Number is the customer-facing reference you would typically quote back to a customer or use in support communications. It's a sequential number assigned to each Case as it's created, giving your team and your customers a simple, human-readable way to refer to a specific support case.
Case ID is a separate, system-generated identifier tied to how Zoho's underlying data model handles the Cases module. This dates back to how Cases was originally implemented, alongside the standard record ID every module in Zoho CRM generates. In practice, Case ID is mainly relevant if you're working with the API, custom functions, or integrations that reference records by this identifier, rather than something a support agent typically needs to quote to a customer.