R1 = R2 = 50 ohms are just to give reasonable terminations for the input and output.
In parallel with each of C1 and C2 are 100 ohms (series combination of 50 ohm source and R1, and 50 ohm load and R2).
Large values of C1 and C2 in parallel with 100 ohms are approximately equal to similar values of C in series with much smaller resistances.
(See series-parallel transformation for impedance/admittance in elementary textbooks.)
Therefore, you end up with a large capacitance and small resistance in series with the inductor under test.
You drive the left side (R1-C1) from a variable frequency sine wave: this could be an AWG, the tracking generator of a spectrum analyzer, the source of a VNA, or other AC generator.
You can see the output at the right side (R2-C2) on any measuring device you want, with a 50 ohm termination: voltmeter, oscilloscope, spectrum analyzer input, VNA, etc.
When the inductor self-resonates (parallel resonance), the total impedance across it is much larger than the impedance at R2-C2 and the signal will be a minimum.
I have never posted anything on YouTube, but I have used this circuit to measure inductors.
I just mounted two BNC connectors on a single-sided circuit board, with the two capacitors mounted on appropriate stand-off insulators to fit the inductor.