ELI5: Explain Like I'm 5

Indexed unit of account

An indexed unit of account is a way of measuring how the value of something changes over time. The index measures how much something is worth when compared to how much it used to be worth. For example, if a pizza used to cost $1 and now costs $2, the index would measure that it has gone up by 100%. This way people can see when things become more expensive or go down in price.