What does it mean when a website is ''cached''?

I know this is probably simple, but I really know nothing about computers, how the Internet works or any of its terminology. So I’m all lost now.
The problem is a website I usually go to, but for two days now it says the address isn’t valid. I’m guessing it crashed or something, but when I google search it, it always says cached for every result. Does this have anything to do with anything?
And now I’m not gonna Google it so shup foo.
Joking. :p—And thanks for thy time.