What does it mean that the sun will evolve into red gaint and white dwarfs

After about 5 billion years, the Sun will run out of hydrogen fuel in its core. Without the outward pressure from hydrogen fusion, the core will begin to contract under gravity, causing it to heat up. This increased heat will cause the outer layers of the Sun, which still contain hydrogen, to expand dramatically and cool down, making the Sun appear redder and much larger. It will swell up to engulf Mercury, Venus, and possibly Earth.

After the red giant phase, the Sun will shed its outer layers, forming a beautiful planetary nebula. The remaining core, which will be extremely dense and hot, will be left behind. This remnant core is called a white dwarf. It will no longer undergo nuclear fusion but will slowly cool down over billions of years, eventually becoming a cold, dark black dwarf.