What does the consumer price index measure ?

The CPI is defined as a statistical estimate of the value of something many years ago as compared to the current time.

Like if you purchased something in 1990 for $10, so what is the value of that thing in current time. Its the comparison of basically currency. That time, the value of $10 was very high as compared to today's time.

So, this is the difference that is measured by CPI.

This is based on inflation and this is the reason, there is a gradual change in living standard.

i get you, what you should do is think of the positive things that would come out of it. it will make yours parents proud and raise your grade. you should always try and if you can't focus tell the teacher.