ELI5: Explain Like I'm 5

Hyperreal number

Hyperreal numbers are numbers that are bigger or smaller than regular numbers. They are used when you need numbers that are very big or very small. For example, if you were trying to measure how far away a star is, it may be so far away that you need a number that is so big it is impossible to write it out. Hyperreal numbers help us to measure things like stars that are too far away to measure in regular numbers.