What is "praecognita"

Praecognita \Pr[ae]*cog"ni*ta\, n. pl. [L. praecognitus, p. p. of praecognoscere to foreknow. See Pre-, and Cognition.] This previously known, or which should be known in order to understand something else.

n. Things previously known, or which should be known in order to understand something else.