Comparing the different Intel product lines is a little like comparing different models of cars. You can get just a basic Ford Fiesta with no options that will get you around town and not much else. That's going to be the Celeron, a basic processor without high operating frequency, big caches, no hyper threading, or overclocking. You can spend an extra $8,000 and move up to the Ford Fiesta ST and get the high performance engine, suspension, tires, power everything, upgraded brakes, transmission, and fancy interior gadgets. That's going to be the Core i3. it's a Fiesta, but modified to make it faster, and just better all around (adds an L3 cache, hyper threading, and a higher operating speed). Now if you want to step up, go get a Ford Focus ST. A Focus with go-fast bits added to it. That's like the Core i5 and i7, double the cores (i7 adds hyper threading and a big cache), enables over clocking, and a pretty significant boost in performance. Of course you'll pay extra for it, but that's the price to pay for performance, just like with a car.