What is not very effective against dark

Well, it depends on what kind of dark Pokemon it is. for example, if you had a dark garados and knowing is would be water dragon and dark, you would just match up the sub catogory. so in this case, a fire Pokemon would be weak, but it doesnt matter. you just have to match up their sub catogorys. hoped i helped! PS im a twelve year old girl. impressive, huh?