Whats the difference between high-use academic words and key terms ?

fall into three tiers.
Tier 1 words include basic or high-frequency vocabulary words and usually don’t include multiple meaning words.
Tier 2 words are less familiar to students but help in comprehending written texts and conversations shared between the teacher and student. Tier 2 words are “general academic words” and sometimes may be referred to as “rich vocabulary.” These words are precise but more subtle forms of familiar words and include multiple meaning words. For example, instead of saying “he walked,” one may say “he sauntered.” Tier 2 words cross over into a variety of domains or subject areas.