If you take 100 joules of electrical or chemical energy, and then direct them to a heater in a house, it'll create about 100 joules of heat. That's 100% efficiency.

But if you use the 100 joules of energy to run a heat pump, it might bring in 300 joules of heat into the house. That's 300% efficiency, when measured locally at the place you actually care about (inside the house). Zoom out and laws of thermodynamics still make it impossible to create more energy than was put in, but if you look at just the part you care about, it's possible locally.