CPI vs. GDP deflator

CPI (Consumer Price Index) the most commonly used measure of inflation. Why of all methods is this most popular? An average household… what is that supposed to be? Every country can support numerous cultures of which each can have its own “average”. Why only account for a section of the economy to calculate the inflation for the ENTIRE economy? Shouldn’t we be looking at EVERYTHING to account for EVERYONE?

What are CPI and GDP deflator?

Which one is better?