Difference between equivalence and implication
First, to answer the question in your question title: the difference between equivalence and implication in CTL formulae is the same as the difference between equivalence and implication in propositional logic, that is, $A \leftrightarrow B$ is the same $(A \to B) \land (B \to A)$. 

But your real question is whether $\mathrm{AG}\,(A \land B)$ is equivalent to $\mathrm{AG} \,A \land \mathrm{AG}\,B$. To solve this question, you have to look at the semantics of the operators AG and $\land$; that is, what do $\mathrm{AG}\,\phi$ and $\psi_1\land\psi_2$ mean (for arbitrary formulas $\phi,\psi_1,\psi_2$?

The semantics of CTL works via transition systems. Two formula are equivalent if they are true in exactly the same transition systems and states. Looking at the semantics of AG and $\land$, it should be fairly easy to decide whether there is a transition system where the one formula is true and the other isn't.