Junk resources store info on specialized commodities that can be bought and sold at only one location (each). The fields are:
SoldAt ID number of the stellar object where the commodity is sold
BoughtAt ID number of the stellar object where the commodity is purchased (or -1 for none)
BasePrice The average price of the commodity (works much like the base prices for "regular" commodities)
Flags Misc control bits (all but one unused)
0x0001 Tribbles flag - When in your cargo bay, the commodity multiplies like tribbles.