Hertz devised an oscillator made of two polished brass knobs separated by a tiny gap. Each one was wired to an induction coil. With the juice on, sparks jumped the gap between the two knobs. Those sparks, Hertz hypothesized, would — if Maxwell was right — generate electromagnetic waves. It was the first designed transmitter.
For a receiver, he made a wire loop with tiny knobs on opposite sides of a small gap. He placed this device a few yards away. The two devices were not wired to each other, but sure enough, sparks in the transmitter produced sparks in the receiver.
Hertz had demonstrated that Maxwell’s waves exist. He went on to time them, demonstrating that their speed of transmission is, as Maxwell had also predicted, the speed of light.
It is on his shoulder, and the shoulders of so many others, that we stand today with our progress and knowledge. What we accept now as "obvious" were not so, and took the ingenuity of people like him to discover and innovate.