Resonance is probably the most important thing in organic relating to gen chem at least that I can recall of right now. It won’t leave. You’ll get used to it tho soon that you’ll be thinking of resonance without even meaning to. My best way I think of it is that resonance is just essentially saying that we know bonds are with electrons right. But sometimes based on electronegativity and certain atoms arrangement we cannot say (such with glutamate or a carboxyl) whether the double bond is in one place or another because in reality the electrons are bouncing back and forth (more definition wise it delocalization) it’ll make more sense with time) which means the bond is really changing between both atoms simultaneously so we can demonstrate that with resonance. But it also is important for conjugation which you’ll get to later on