Have you ever wanted to find a bio of someone who's no longer with a company? Or the company went belly up and no longer has a website?
Yes, Google keeps a cache, or snapshot, of websites at the time of indexing. However, Google indexes the web quite often, so these copies seldom go back further than a few months.
That is where the Internet Archive comes in. They maintain something called The WayBack Machine. You can enter a URL and find an earlier version of that website. They don't have everything that's ever appeared on the web, but it is quite an impressive database. At last count, there were 85 billion web pages archived since 1996. FYI, the WayBack Machine does not have a decent search capability, so it's best if you know the base URL of the website that you want to check, enter that & then browse from there. This works well for finding bios of executives who are no longer with a firm, or for finding info on a now-defunct company.