ELI5: Explain Like I'm 5

Star (classification)

Stars are big, bright objects in the night sky. Scientists classify them according to their size, temperature and brightness. Small, cool stars like the Sun are called "main sequence stars". Bigger, hotter stars are called "giant stars", and even bigger, hotter stars are called "supergiant stars"! The color of a star can also help us classify it. Blue stars are usually very hot, while red stars are usually cooler.