How is a protostar different from a star?

Answer 1

A star begins its life as a ball of gas and dust. Gravity pulls the gas and dust into a spere. As the sphere becomes denser, it gets hotter and eventually reaches temperature of about 10,000,000 Celsius in its center. As hydrogen combines into helium, energy is released in a precess called neclear fusion.

Answer 2

A protostar is different from a star in that a protostar cannot be seen because it is enveloped in dust. Unlike a star, a protostar does not have any fusion in its core yet.