Explain the difference between a protostar and a star.

Protostar vs. Star: What's the difference?

• Protostar: This is like the baby stage of a star. It's a big ball of gas and dust that's just starting to form. It's not hot enough yet to start nuclear fusion, which is what makes stars shine.
• Star: This is the adult stage. A star is a super hot, glowing ball of gas that's creating its own energy through nuclear fusion in its core. Think of our Sun – it's a star!

In short: A protostar is still forming and not yet shining from fusion, while a star is actively fusing elements and glowing.