Here's a breakdown:

* Current Age: The Sun is approximately 4.6 billion years old.

* Main Sequence: The Sun is currently in its main sequence phase, where it fuses hydrogen into helium in its core. This is the longest and most stable phase of a star's life.

* Red Giant Phase: In about 5.4 billion years, the Sun will run out of hydrogen fuel in its core and begin to fuse helium. This will cause it to expand into a red giant, engulfing Mercury, Venus, and possibly Earth.

* White Dwarf Phase: After the red giant phase, the Sun will shed its outer layers, leaving behind a dense, hot white dwarf star. This white dwarf will slowly cool and fade over billions of years.

It's important to note: This is a simplified explanation, and there is some uncertainty in the exact lifespan of the Sun. However, the 10 billion year estimate is based on current scientific understanding and models.