For the game Starbase Orion: What does economic hoarding actually do?
From the game description, Economic Hoarding stockpiles your production for future use.
Let's say your planet produces 10 production points per turn. If you set the planet's build queue to Economic Hoarding, it stores 10 production points per turn. If after 2 turns you make the planet build a colony ship, the stored 20 production points are then automatically added to the production of the colony ship. Essentially, this is an option for you to build something in advance.
This is in contrast to Economic Funding, which as Shadur has commented above, converts production to money, in a 2:1 ratio.