My cousin takes his education tooo extremely. Thats a different story.
He is taking college courses ever since he started high school. Up to right no he is a sophmore and has 16 credits so far. (I dont understand "credits" explain if u can XD ).

What are the advantages?
Should I do this too?
What are credits?

Taking college credit courses while in high school will help you cut back on the number of classes or credit hours needed to graduate. Each college class is assigned a certain number of credit hours i.e- english composition is 3 credit hours. Once you get into college there are a number of credit hours that need to be met in certain subjects in order for you to graduate with a certain degree. Most of the credits or college classes you will take in high school are lower level credits or base classes like english, spanish or foreign languages. Some high schools let you take upper level math for high school like AP calculus. Once you enter into a university most students are required to take so many credits in english, math, social sciences, etc. regardless of a major. So basically to answer your initial question- yes, take college credit courses in high school, it will benefit you later on. You don’t need to take all the classes offered for college credit while in high school, but every bit helps. Good luck!