Modifiers are words or phrases that increase or decrease the strength and universality of your main point. For example, (to pick a random topic off the top of my head) instead of saying 'Vegans are self-righteous blowhards' or 'Carnivores are defensive and aggressive', you can say 'Some vegans are self-righteous blowhards' and 'In my experience, many carnivores can sometimes get defensive and aggressive.' The modified statement is more likely to be true, and less likely to cause offense.