I'm not quite sure that I really understand WHY I need to use implication for universal quantification, and conjunction for existential quantification.
Let $F$ be the domain of fruits and
$$A(x) : \text{is an apple}$$
$$D(x) : \text{is delicious}$$
Let's say: $$\forall{x} \in F, A(x) \implies D(x)$$ Is correct and means all apples are delicous.
Whereas, $$\forall{x} \in F, A(x) \land D(x)$$ is incorrect because this would be saying that all fruits are apples and delicious which is wrong.
But when it comes to the existential quantifier: $$\exists{x} \in F, A(x) \land D(x)$$ Is correct and means there is some apple that is delicious.
Also, $$\exists{x} \in F, A(x) \implies D(x)$$ Is incorrect, but I cannot tell why. To me it says there is some fruit that if it is an apple, it is delicious.
I cannot tell the difference in this case, and why the second case is incorrect?