A Harvey water softener is a device about the size of a computer tower. It gets plumbed in to your house and it takes the water as it comes into the house and runs it through a pair of softening tanks, which remove the minerals from the water that cause limescale and soap scum. 

Every so often, the machine flushes the minerals from the tanks by rinsing them through with salt water, which is why it needs to be kept topped up with blocks of salt. Aside from that, you don’t need to do anything to keep it running.