Are the main differences between whey protein and whey protein isolate that isolate contains no fat and higher concentrations of protein? Or is there more to it?

I have two brands, Hammer (whey protein isolate) and Trader Joe's (whey protein). They have similar amounts of protein but the TJ brand has 2g of fat. I'm not really concerned with the fat but if there's something I'm not understanding, I'd like to be educated. Otherwise, I will continue to purchase and use both.