A Textmode Driver is a type of Driver that is only used during the intital Setup program (I.e. When it's detecting basic Bus, and Periphiral devices, as well as Stroage Drives.)
Textmode and PnP drivers differ, in that Textmode isn't optimised for Speed, rather compatibility. For example, SCSI, RAID and SATA Drivers can both come in Textmode and PnP Varieties.