Do I need two Visas, or just one to enter the P.R. of China from Hong Kong? What type Visa?

I plan on visiting the mainland of China as a tourist in mid October of this year. I plan on landing in Hong Kong before entry into the P.R. of China though. I am only doing this to reduce the air fare required to get there. Will this require me to have a Visa for both Hong Kong and the mainland? Also which type(s) of Visa will I be required to have to do this?

Thanks,

Steve Calhoun