The build is a standard facing-transducer levitator, but the treatment is unusually thorough on the driving circuit. It starts with the tone function, moves to finding the resonant frequency, then to driving the transducers directly from Arduino pins, and shows that working badly before introducing an H-bridge and then an external supply and an inverter. The chapter markers in the description map each of those steps.
That sequence is the value. Plenty of levitator tutorials present a finished schematic; this one shows the intermediate versions and why each was insufficient, which is how you learn to debug your own.
Parts list, circuit diagram and code are on the Science Buddies project page linked from the description, and the whole thing is framed as a science fair project, so the documentation is written to be reproduced rather than admired.