"When installing and using Linux, your drives appear as devices with the following names: hda--first IDE drive (stands for "hard drive a", i.e. the master drive on the first IDE interface), hdb--second IDE drive (i.e., the slave drive on the first IDE interface), hdc--third IDE drive (i.e. the master drive on the second IDE interface), hdd--fourth IDE drive (i.e. the slave drive on the second IDE interface). The numbers mean the partitions on the physical drives: "hda1" means the first IDE hard drive (hd a), first partition (1); "hda2" is the first IDE hard drive, second partition; "hda3"--the first IDE hard drive, third partition; (and so on if you have more than 3 partitions on the first IDE hard drive); "hdb1"--second IDE hard drive, first partition (or just "hdb" if it is the CDROM installed as a slave on your first IDE interface). "hdc1"--third IDE hard drive, first partition, etc. SCSI drives have analogous names but start with the letters "sd" (="SCSI drive"), followed by the letter indicating the SCSI interface and by the number indicating the SCSI device id. For example, "sda4" means "first SCSI interface, id number 4". If you have an external zip drive attached to your parallel port, it will appear as SCSI device "sda4" (zip drives work in a SCSI-emulation mode)."
Copy/Paste from http://linux-newbie.sunsite.dk/