The OKI ML1120 is a dot matrix printer, typically used for printing forms, invoices, or other types of documents that require impact printing (e.g., multi-part forms). The OKI ML1120 Windows driver is the software that allows your computer running Windows to communicate with and control the printer. Without the appropriate driver, the printer might not function properly, or it might not be recognized by the operating system at all.
Here's a general guide on how to install the OKI ML1120 printer driver on a Windows computer: