hi Jessica afraid of means scared of e.g. I am scared of spiders. afraid for has a completely different meaning, it means that you are scared about the well being of that person or thing e.g, I am afraid for my health but i think afraid for is not used a lot because there are better ways to express the same thing e.g. I am worried about my health

those are sucke a phrases the best way to learn them is reading phrasal vers in use which written by Michael McCarthy