The meaning of "raw materials" 
Stars are the most important objects in the Universe--huge balls of gas that grow dense and hot enough to sustain nuclear fusion in their core. They are the ultimate source of all high-energy radiation such as visible light, and also the means by which the lightweight raw materials of the universe (see page 394) are transformed into heavier and more complex elements--including those that make up our own bodies.

In the context, I think 'raw materials' as 'an element' in physics such as hydrogen and helium. Or, maybe raw materials just mean matter or particles of matter. Could you explain them?
Embarrassingly, but to be frank, I have no basic knowledge of physics and I'm not an English-native speaker. 
 A: It seems the author of that document is intending to mean electrons and protons.
After collapsing upon itself, a cloud of (molecular) hydrogen gas can form a star. From the various fusion processes (starting with the proton-proton cycle or the "CNO" cycle), elements up to (and sometimes beyond1) iron can be formed. During the explosion of the star (the event is called a supernova), the (former) star goes through a process called supernova nucleosynthesis in which elements heavier than iron can be formed.
Since it is the hydrogen gas that (eventually) make all other elements, via fusion processes, then it should be the protons and electrons that are the "raw elements" the author speaks of, as hydrogen consists of a proton & a electron.

1. The answer by Rob Jeffries is a bit technical
A: As the text says "the lightweight raw materials of the universe (see page 394) are transformed into heavier and more complex elements" I would guess that the table 394 is a list of light elements, probably Hydrogen and Helium mostly. 
Of course, looking at the table we won't need to guess. 
These elements are used by the star to "build" heavier elements.
The analogy is with the industry meaning of the term "raw material" which can be anything which is taken by a factory and converted into something else. For example, wood id raw material for a paper factory and paper is raw material for a printing house.
