what are accumulation points in easy terms? and how do we use them? I've read the definition and have seen videos where they all say the same thing. We have a $\epsilon$ neighborhood around $l$ and if it contains another point, let's say set $A$, other then $l$, then we call $l$ an accumulation point of $A$. But what's the point of this? why do we need accumulation points? and is my description correct?

Your description is not correct. You say: "We have an epsilon neighborhood". The definition says: "For every epsilon neighborhood".
The answer to "Why do we need them" is not easily summarized here. Suffice it to say, this is one way to think about convergence, closeness, separation, and related ideas. Its value will become apparent as you continue to study topology.
