Cookies what are they and how do u know they are cookies

Cookies are little files that hold a small amount of data about certain activities ie, to tell the internet browser that you logged onto Myspace so that you don't have to keep logging in every ten seconds, it's kinda like a memory for the website that stays local, in most cases Cookies are fine but sometimes they do slow a browser down. and try not to double post, you can just edit your first post