Determination is a mechanical term and type of Test.Determination Tests are the most varied of tests and include determining Damage Totals, Ability outcomes and many others.
To perform a Determination Test you take the Determination Dice as stated on the source of the Test, as well as any relevant Bonus Die. Roll them and add together their Results along with any Static Bonuses to get the Total of the Determination Test.
This Total determines the effect of your Determination Test, be it creating an amount of Items or dealing an amount of Damage
Example: [Crafting] D4 Med-Pacs or taking your first instance of Exhaustion would cause a Determination Test with a Determination Die of D4. Dealing 2D6 Damage would require a Determination Test with Determination Dice of 2D6.