lareya, it allows you to connect USB peropherals like the keyboard, USB memory sticks, USB harddrives and USB mouse to the Zaurus 6000L via the cable. The cable just acts as a adapter between the Mini A USB port on the zaurus underside to the normal USB female port on USB cable on peripherals.
Note : see the 6000 hardware forums for keyboard and mouse setup and the iRiver USB host cable that the_oak mentions.