Esau is the eldest and a hunter. Not a particularly good hunter, but he roams out and kills the beasties for meat. He also dresses something like a wild man in animal skins and furs. Isaac likes Esau best. Probably a bit of fatherly envy, there as he would have liked to have been the same way, out hunting instead of tied to the fields and flocks.
Jacob is the homebody, and Rebekah’s favorite. It always figures that Mom and Dad have their respective favorites. Jacob is the guy who stays at home tending the flocks and fields and even doing the more domestic work. The story makes it clear that he’s something of a momma’s boy.
Now, a little bit of math is in order. See, the way that inheritance worked back in ancient Hebrew culture was a bit different than we might imagine. It’s not actually difficult, it just requires a couple of extra steps. With two sons, it seems that it would be an even split between them, but that’s not the case. There is this thing called the birthright, and this is part of the reason why Sarah sent Ishmael and Hagar away. So, take the total number of sons (sorry, ladies that’s just the way it was) and add 1. So, for Isaac’s sons, it’s Esau, Jacob, +1 for a total of 3. Now, take Isaac’s total assets and divide by that total, so everything is divided into 1/3 shares. Esau gets 1/3, Jacob gets 1/3, and then there is what is called the birthright share, which is given to the eldest. So, in reality, Esau will get 2/3 and Jacob gets 1/3.
For Ishmael and Isaac it was the same thing. Sarah didn’t want Isaac to get a measly 1/3, so she cut out Ishmael and Hagar completely.
Why do we care? Well, it turns out that this birthright is the crux of the story between Esau and Jacob.