It's my understanding that the MacBook is a very, very low wattage part - the "core M" series (~5 watts?). A MacBook Air has the lower wattage "core i" series part (~15 watts?), and the MacBook Pro has the higher wattage "core i" series part (~25 watts?).
The MacBook has an i5 or an i7, yes, and it also has fans, so it doesn't throttle so heavily on high workloads. It makes playing some games on low settings possible, which I appreciate.
I can't find any documentation ATM.