The judge makes findings of law. The judge interprets the law, rules on the law, and issues judgments based on the law and his own understandings.
The jury (if there is one) makes findings of fact. (If there is no jury then the judge also does this.) Finding of fact means evaluating the evidence and deciding if there was in fact an actual violation or if there was not. When I have served on juries it is mostly about if the thing happened or not, or if the action rose to the level involved. In one case the law for one charge involved a pattern of behavior, but all we had in evidence was a single instance of behavior, so I argued that was not met. In civil cases there is often a claim of quantum meruit, that's Latin; quantum = smallest unit or step, meruit = earned; in other words, even if the person didn't earn the large financial reward the jury needs to answer if the person earned even the smallest reward.
Jury nullification is where the jury decides that a thing is not a crime or does not apply. It may happen that a jury may decide even though the people did fight it was reasonable for the situation, thereby nullify a claim about assault even though the assault clearly happened. Or the jury may feel sympathy toward a drug user, and nullify a claim about drug possession even though the act clearly happened.
Usually it is not about the jury sitting in the room declaring "We're going to invoke jury nullification!" Instead typically the jury decides that they don't feel good about a conviction, or decides that even though it looks like the violation happened they don't feel like it rises to the level of the claim, or much more rare, decides the legal claim is wrong or invalid or stupid and votes against it out of principal, which happened several times during racial segregation where juries refused to convict over laws aimed at a minority race. They don't say anything about nullification, they simply return a verdict saying "no" to the claim or "not guilty" to the charge.