An adjective in attributive position is “the good word”. An adjective in predicate position is “the word is good“.
An adjective in attributive position is articular (cf. predicate adjective). Study chapter 9 in BBG.
ο αγαθος λογος
τον αγαθον λογον
ο λογος ο αγαθος
τον λογον τον αγαθον
An attributive adjective must agree with whatever it is modifying in gender, number, and definiteness. Study this document or this video.
A predicate adjective precedes the noun it modifies. It must agree with this noun in gender , number, but not definiteness. video
A substantive adjective will be performing some noun function. video