Is Wahhabism the same as Sunniism? If not, how do they differ?

I know that Wahhabis follow the teachings of Sheikh Muhammad Ibn Abdul Wahhab but I don't know exactly what his teachings were. Years ago when I was in KSA I studied his life story but not his teachings. Saudi history books mention him as a great man who guided the Muslims of KSA to the right path. What do you lot know of Wahhabism? Are Wahhabis a completely different sect or are they the same as Sunnis? I'd also like to know what fellow Sunnis think of Wahhabism (those who know what it's teachings are).