Check the *block schedule* online.. Eg -
www.dictionary.com It explains it better.
Unweighted GPA is Your *real* GPA without any APs (Advanced Placement classes). Many schools outside the US do not offer these AP classes.
Weighted GPA includes those APs and this score is usually above your total GPA...
For example, if the total GPA in your high school is 4.0, then Your unweighted GPA can never exceed 4.0 Eg - 3.8/4.0 but your weighted GPA coulbe 4.5...etc
If you need more help, ask your Guidance counselor. She would know more on it. NOTE: most schools outside the US do not use the Weighted System. So if you do not use it, dont worry about it.
(just curious, what country are you from...? your sign in name seems Nigerian...am I right?)