A DID number, or Direct Inward Dialing number is a genuine phone number that is generally used to route calls directly to a specific phone extension, phone line or mobile phone within an entire organization. DID numbers are often used by businesses and organizations, to allow employees or departments to have their phone numbers, which can be easily reached by external callers.

In the context of a cell phone, a DID number refers to a virtual phone number, used to route calls to a specific cell phone or a group. This can be useful for businesses that need to have a strong local presence in multiple areas or for individuals who want to have a separate phone number for professional or personal use.