That means it has 4 CPUs (If I have it correct, it has two chips with each of them 2 cores).
You can run that server as one LPAR running all four CPUs
or (with an HMC) partitioned into 4 LPARs each running 1 CPU or (with an HMC and the APV feature) up to 40 SPLPARS each running .1 CPU.
That last number is a configuration maximum, you'll be limited by other factors (CPU need per LPAR e.g. one or two VIO servers will be using more than .1 CPU - typically .5 CPU - and also the amount of memory you have to share among the SPLPARs)
HTH,
p5wizard