If your refrigerator has an ice maker or filtered water spigot, then it will typically be supplied by a cold water shut off valve behind the refrigerator. This valve is traditionally located in a recessed, open-front plastic box.
When the valves have to be replaced, sometimes it can be done inside the box itself. Other times, some of the drywall directly below the valve has to be removed to access the pipe lower down.
In some larger homes with built-in refrigerators (like some of the Sub-Zero models), the shut off valve may be located in an adjacent cabinet or underneath the kitchen sink due to the refrigerator being too large to readily move by hand.