what is an Authority Amazon site?

Can someone explain me the difference between an Authority Amazon site and a simple Amazon Niche site?

I thought that maybe
Amazon niche site = best tapis roulant
Authority Amazon site = Best fitness machines

A very high quality website that is respected by knowledgeable people in its industry. It is a website that has content on it that is so good and makes the site so useful that people are actually glad they landed on it and want to share it with their friends.

Simple answer: Authority targets a multitude of keywords (broad) and required much attention (seo etc). Niche targets core focused keywords (niche) and not difficult to rank as compared to Authority site.

G00gle is your best friend here so do some research, BHW too .. all the best