Penis size. The vacuum is only temporary. Your size is your size after puberty. There is no good way to increase penis size, despite the television and magazine ads. One of the few exceptions is if you are overweight, you lose about 1" for each 10-20 pounds of extra weight you carry around, so weight loss can be helpful. Satisfying your partner is about much more than penis length.
Temporarily, yes. Vacuum pumps will temporarily draw blood into the erectile chambers of the penis and increase its size, but this effect will not last long term. Surgeries can increase penile girth and give the appearance of a longer penis as well. Long term stretching of penile tissue has been shown in some studies to increase size too.