Looking at plumbing in a house have you ever wondered what different things are? There is that usual loop of pipe, which for no apparent reason loops down from ceiling in the basement?
Or the two copper pipes about a foot apart one above the other that are sticking straight out and capped off?
The answer is, they are what is called “a pre-plumbed hook up” for adding a water softener, they are often installed buy a builder for an additional fee when the house is being constructed .
They are typically found close to the water heater.
If you are buying a home and the water pipes are CPVC (a cream colored hard plastic the same as the photo) don’t waste your money paying the builder to install the dropped loop, unless its been done for free.
As you can see, it is not something that would be difficult to do yourself or for your plumber.
If you are having a new softener installed most companies will install it and add the connection pretty much doing it for free.