Like the arc/solar/void damage types? They have a pretty minimal effect. I'm sure you've seen at least a few of the enemies with the energy shields? Blue shields are weak to arc, orange shields are weak to solar, and purple shields are weak to void. Other than that, they usually only matter on the weekly nightfall strikes, which have modifiers called [arc/solar/void]burn. The burn doubles the damage of all attacks of the corresponding type, both your attacks and your enemies'.