Electronic – Peaking Inductance

That looks like a 220 µH inductor. These size inductors (like a lot of electronic parts) are labeled with something a lot like a floating point format in a computer. The first N-1 digits are the mantissa and the last digit is the exponent of 10 to apply to the integer mantissa value. In this case, the mantissa is 22 and the exponent 1. The value is therefore 22 x 10^1 = 220. The fact that the units are µH is obvious from the general size and windings. Some very small inductors are labeled like this in nH, but this one is obviously a lot bigger than 220 nH.

M is the number of distinguishable signaling states that the channel can pass, usually modeled as voltage levels.

For example, if you can transmit one of four different voltage levels over a pair of wires, you can send two bits at a time. Eight levels gives your 3 bits, and so on. This is why there's a log₂ relationship between levels and bits.

Distingiushable means that the receiver can reliably determine which of the levels the transmitter is sending. This means that the voltage offsets introduced by noise, intersymbol interference, etc. are less than the actual separation between the signaling levels at the receiver. As the noise level goes up, either you need to increase the overall signal level a corresponding amount, or you need to reduce the number of signaling levels you're using — either way, you increase the separation between the signaling levels.