USD/CHF is the pairing of the US dollar against the Swiss franc.
It shows you how many Swiss francs you would need to purchase one US dollar. The first currency in the pair is the base currency – so in this case it would be USD. CHF is the second currency, so it is the quote currency.
For example, if the price for USD/CHF is at 0.99 this means it would cost 0.99CHF to purchase 1USD.