What does the 65mph on the freeway actually mean?

I'm Swedish and currently on holiday in LA

Just earlier today I drive on the freeway, going 65mph as per all the signs

But I kid you not, literally everybody was flying past me going at least 80mph+

I stayed in the right lane though

So what does the 65mph actually mean?

Is it just a suggestion and you're allowed to drive 15-20mph faster than it?

Or is there some insider knowledge I'm missing here? 🤣