The cache exists because of a basic assumption made by browser designers: the internet is slow. More accurately, your internet connection is slower than your computer.
What that means is that it’s faster to get something from your computer's hard disk than it is to get it from the internet. Even with today’s faster internet speeds, that still holds very true.
Browser designers noticed that most web sites had many of the same elements on multiple pages. For example, if you look at this page, you’ll see the CoLab's logo at the top. It’s actually at the top of every page on this site. So the thinking was, why download the same logo for every page? Why not just download it once and then keep it so we can use it again?
That’s what the browser cache is for. The cache is nothing more than a place on your hard disk where the browser keeps things that it downloaded once in case they’re needed again.
When you first visit a page on this site, the browser downloads the logo into the cache, and then displays it on the page you’re viewing. For each additional page you visit, the logo doesn’t need to be downloaded again; as long as the same logo is displayed, it’s already on your hard disk.
The cache has a size limit, which you can usually configure. When the cache gets full, the items in it that haven’t been used in a while are discarded to make more space.
And it’s all behind the scenes for you, until something happens.
When websites get updated, like CoLab was yesterday, your computer may be holding on to info that the last version saw. For example today I couldn't see what files looked like in my file viewer.
If this fails to solve your issue, then its time to let your techie know of your issue, don't forget to let them know you've tried a 'hard refresh', it'll impress them and saves you from having to do it when they ask!