SRM 7.0 contract type qty/valu based and scheduling agrement

Hi Team,

I want to know in SRM 7.0, about contracts. I searched in help. but i didn't get correct information about like value/qty based contract,

what is normal contract? what is scheduling agrement in SRM?   what is the main difference.

The difference only comes in MM system or in SRM ssytem also.

Kindly provide the inforamtion and also links .

Thanks,