My cookies are comming out like a cake or brownie?

I am having a problem, i baked some cookies, and followed the recipe to a T (basic chocolate chip), and the cookies baked fine, but when they came out, they came out not gooey or chewy but more... fluffy textured inside, like a cake or muffin top, I remember once before when I used to live at home, the SAME thing happened with some oatmeal cookies i made. Im wondering what I did wrong...

You didn't blend the ingredients together but rather whipped them together throughout the mixing process after the eggs were added, thus incorporating more air. This caused the dough to become more leavened upon baking.

There's a difference between folding, blending and whipping. How you mix the ingredients and the manner in which they are added are as important as the ingredients themselves.