It's buried in this thread, but Jarred explained it.
RED STATION is a base unit that connects via eSATA, FW800 or USB (for now, other interfaces as they become available). You can connect up to 4 media interface modules to it. So it is for offloading or interfacing to RED media. As an example, you can connect it via SATA and have two CF reader modules as well as a reader for 1.8" SSD mags and one for 2.5" SSD mags.
Would be good if the base unit interface was also modular in the sense that we can add say Light Peak or FW1600/3200 if/when they come out, without having to buy a whole new base unit?