The Proton-Proton Chain

The Sun generates energy in its core by converting hydrogen into helium via what is known as the proton-proton chain. There are several ways in which hydrogen can be converted into helium. More massive stars, for example, use what is known as the carbon-nitrogen-oxygen (CNO) cycle.

The basic proton-proton chain is quite simple.
The full proton-proton chain is more involved but is still pretty straightforward.

An important point to notice is that the proton-proton chain not only produces energy, but it also is a prodigous source of the sub-atomic particles known as neutrinos (and, in particular, the flavor of neutrinos known as electron neutrinos. There are two other kinds of neutrinos known as tau neutrinos and muon neutrinos--More on these things later).