Why fry rice before boiling?
This is sometimes called "pilaf style", though technically actual pilafs do not require the sauteeing step. It is, however, very common in pilaf and related dishes.

The main function of this is to change the composition of the starch on the surface of the rice. This reduces the starches that cross-link and make rice sticky. It helps your rice to cook up into separate grains.

While you're at it, it also adds some flavor to the rice, by caramelizing some of the starches. Plus, it adds oil, which can carry flavors of its own and help distribute fat-soluble flavors in the other ingredients.

The effect is very different from "fried rice", where the starches have already been cooked and gelatinized before frying. The goals are somewhat the same, adding browned flavors and distributing fat-soluble ingredients, but the chemical changes to the surface of the rice itself will be different.