There are three major classifications of NFC communication, NFC-A, NFC-B and NFC-F. Each present their own unique advantages and disadvantages.
NFC Type A is slower than type F but is much cheaper, thus is very popular in common tags sold on Amazon or other online marketplaces. This type utilizes Miller encoding, which is the modulation of a signal from 0% to 100%.
NFC Type B is the same speed as type A, thus is again slower than type F, while also being cheaper. The difference between the two is that type B utilizes Manchester encoding, which is the modulation by increments of 10%.
NFC type F is the only proprietary signaling technology of the three listed, being used solely by the Sony Corporation. This is by far the most expensive tag classification, yet is also the fastest of all three signaling technologies covered.
Miller Encoding
Encoding is the technical process in which data is transformed into machine language and transferred from one NFC tag to another, and can be thought of as the lowest level at which NFC truly communicates. Miller encoding is the first of the two primary encoding styles used in all three of the major signaling types. There are three rules when discussing Miller encoding: If bit is 0, do not invert the signal, if bit is 0 but previous bit was also 0, invert the signal at the edge of the bit, and ff bit is 1, invert the signal at the middle of the bit (this is the delayed transition).
Manchester Encoding
Compared to miller encoding, this style of encoding is much easier to understand. If the modulated signal is at the lower point, this being 10% lower than a higher value, than it is 0. If it is at the higher value, it is considered to be a 1.