CPU.. processor..
http://en.wikipedia.org/wiki/Central_processing_unit
The shared and reseller servers come with 2 CPUs because they are needed to cover the massive load that is hosting 150+ websites on a single machine.
But you're not doing that; you're doing less. Therefore your server only has 1 CPU. If you needed more than one, you could get a fancier (and more expensive) server.