Problems about cookies

[Zephirus]

I have readed the cookies tutorial on w3schools and I noticed some didatical flaws. To somebody that never created a cookie before (like, for exemple, me), the tutorial (http://www.w3schools.com/js/js_cookies.asp) is completly ununderstandble. It uses comands I have never heard of (indexOf, length, what the ###### are these?!?!) as well as unexplaned lines of codes. In some moments, the tutorial text even says what means some piece of code, but not why or how it was made.I'd like if somebody gave me a hand, explaining, for a newbe, how to make a JS cookie and what means the stuff of the exemple (http://www.w3schools.com/js/tryit.asp?filename=tryjs_cookie_username)Thanks.