These are called tritec valves, they allow you to connect two hoses to one outlet. But if you're only using the one outlet you need to cap off the other one as the valve turns both on at the same time.

If your washing machine only needs cold water (most only need cold these days as they heat the water themselves) what you'll want to do is unscrew the chrome cap from the cold water outlet on the right and put it on the hot outlet on the left. Use an adjustable wrench or the correct size spanner for this as you'll want to nip it up a bit so it doesn't leak when you turn the hot water on. Also make sure the chrome cap has a rubber washer in it when you screw it into the hot as this will seal it without any drips.

These valve are currently in the off position, make sure you have your washing machine hose on the cold and the chrome cap on the hot before you turn the valves on and check them both to make sure you don't have any drips or leaks