When commentators refer to currencies being up or down they...

When commentators refer to currencies being up or down they usually mean in relation to the US$ and to a lesser extent a basket of other major currencies.
So the US$ is down, compared to what, some other currencies? A minority of those other currencies might be more "downer" than the US$ at the time as they float along at the mercy of waves and troughs in the monetary ocean.
Basically money is a tool for bartering, simple. To barter you need something of worth. You have to have the goods to barter with that your money represents. Things get out of whack when goverments turn on the printing presses and their money eventually has less and less worth and no relationship to GDP.
In an ocean of worthless paper I'd be looking for somewhere more solid, tangible and permanent to drop anchor.