I'm a new player and I've been watching some videos on how to mod my weapons and I keep hearing the terms "additive" and "multiplicative" damage. What exactly do those mean? From what I understood, Pressure Point and Condition Overload are "additive" damages, while the Smite mods are "multiplicative" damages. Is this right?

Also, a lot of the vidoes say that using more than one mod that adds damage, which I assume to be "additive damage", is bad. For instance, they say I'm not supposed to use Pressure Point and Condition Overload at the same time. Why is that so?

That's quite a lot of questions, but I hope someone can help me. Thanks!