The smart meters replace your old gas and electric meters. As others have said the gadget in your house is just displaying your current usage, it is supposed to help people be more efficient with their energy usage by having immediate access to their consumption in pounds, shillings and pence.
It is quite frightening though when you first monitor it, for example at the moment I have a tv on plus my computer equipment and I am currently using 381kwh or 5p per hour, if i put the kettle on for a brew (which I do a lot) that suddenly jumps up to 50p per hour!
Best to just ignore it, less stressful that way!