Here's why:
* Determiners modify nouns. They tell us how much, how many, or which ones.
* Conjunctions connect words, phrases, or clauses.
Examples:
* Determiner: "Some people like to eat spicy food." ("Some" tells us how many people)
* Conjunction: "I like apples, but I don't like oranges." ("But" connects the two clauses)
Let me know if you have any other grammar questions!