Presuming you are not thinking of Tesla's work on resonant inductive coupling (like a Tesla coil), you are probably thinking of Wardenclyffe tower. That was suppose to be a ground - air conduction system. Many people incorrectly think it is an induction or radio system.

If you think about a classic circuit, electricity flow into one end, round the circuit and returns to the source at a lower voltage.

If you put a button and buzzer into this circuit and stretch to many kilometres / miles you have a telegraph.

The problem with this is your wire has to travel the distance twice. Once when it comes from the source through the button to your buzzer and then it has to go all the way back to complete the circuit.

But people eventually noticed you didn't need to do that. If the wire went into ground after buzzer, telegraph still worked. It was believed the circuit was completed through the Earth. It was also believed that the atmosphere had an extremely good conducting layer that was separated from the Earth. So this is basically two wires.

So the idea was to feed electricity into the ground, it would travel through the Earth, you would put a wire into the ground going through what ever you want to power, and the electricity would flow into the sky and back to Wardenclyffe tower completing the circuit.

This would allow relatively large amounts of energy anywhere on the planet as long as you had a wire. And would have been truly transformational to humanity.

But this doesn't work. We now know that the ground flow rate is extremely limited and drops off fast. But Earth has significant capacitance. So the telegraph lines were just feeding charge into that. The amount that telegraph lines used was low enough that the slow discharge rate didn't impact it that much. That capacitance gets used today with neutral and grounding / earthing lines, they just go into the ground. AC pushes and pulls that capacitance without needing a return path.

So Tesla's idea (and other people who attempted similar) ultimately wouldn't work.

Tesla however did work on resonant inductive coupling which is used on modern wireless power transfer systems, just no where near the scale of what Wardenclyffe tower was meant to achieve. It is extremely short ranged, normally used in lower power embedded circuitry but does have some larger use cases like magnetically levitating vehicles and the Tesla coil.