Type Reveals are resources that will define the resulting sprout for a seed, or the resulting DNA Sequence for Ancient Bones and Seeds.
They can be earned in POIs running with money, bought in the Alienum Main Store, or crafted in a Chemistry Station. The resources that are Type Reveals have the letters TR on its name.
In POIs, some types can be found only in places with specific weather. For example, TR Fire Bloom can be found only in places with temperatures above 40°C, and the TR Frozen Pike in temperatures below -5°C.
Why the need of TR, instead of just giving a seed or bone of certain type? We don't want to have problems with the new gacha policies. Since you can buy or craft the type of TR you want, not only earning, they are not considered random.