The Wayback Machine is crawling the internet, constantly, like Google and other search engines. But this creation backs up archival copies of websites as it crawls. And you may use it yourself, to see what a website looked like at some time in the past.
You might just use this for the novelty of seeing a website (Amazon? eBay?) from many years ago. But the research possibilities here can get serious. Some people use The Wayback Machine to find info that was changed or removed. You can copy the URL from any website, and paste it in to the Wayback Machine’s search field, to see what’s available from back in time.