What do these Quizzes Actually Do?

My mom always tells me not to take the quizzes you find on social media, like the Buzzfeed quizzes that we all know so well.  These quizzes promise to answer any question you have, and also all the ones that you didn't know you even had.  They will tell you where you should go, guess your favorite food, and even tell you what TV show you are. There are thousands of quizzes like this, and they can be a fun way to pass a few minutes when you are waiting for something, or trying to procrastinate. However, my mother always told me not to take them, due to the fact that they are just a way to gather your information. However, I had no idea how true this actually was, so I decided to look into it.  According to an article by Local 8 News, some of these quizzes are designed by hackers who want your data, or who want to get you to visit another website and give them data there, or share it with your friends.  However, the article also said that not all quizzes do this, and if you take a few precautions, it should be okay.  They advised that you make sure you trust the company or person that created the quiz, check your sharing settings, and make sure you don't give out any personal information. 
I did check my sharing settings, and made sure that everything that I didn't absolutely need to be sharing wasn't being shared.  I am also careful about not taking any quizzes anywhere that require information about age, gender, location, or any other information like that that I don't want strangers knowing.  However, I don't really see a huge problem in choosing the dog that looks the cutest, or the food that I'd most like to eat. I do see where that information could be used to narrow-cast ads towards me, as explained in The Persuaders, but I personally feel that if I try not to share any information at all, I will simply be avoiding all forms of social media altogether, and while that may be a good thing, its not something I'm ready for quite yet.