In the proton-proton chain process the mass of four protons is slightly greater than the mass of a helium nucleus Explain what this difference in mass means for a star like the Sun?

Answer 1

It means that when 4 protons fuse into a helium nucleus, the difference in rest energy per nucleon escapes as a series of photons (and some other particles that are less relevant to your question). This is the source of sunlight.

Answer 2

This mass difference is converted into energy through the process of nuclear fusion, providing the Sun with the energy it needs to shine and sustain life on Earth. The released energy balances the gravitational forces to keep the Sun stable and prevent it from collapsing under its own weight.