Intel Video Shows How It Makes a 10nm Processor

tl;dr: Mostly marketing term today. Nonetheless, the changes TSMC made are much more incremental, for example the 12nm is more of a variant of the 16nm than a full new node. Once again, this is very very expensive because the cost to equip a modern fab passed a billion dollars long ago and now runs into tens of billions. Mostly Apple is the reason TSMC could do this without going bankrupt. Also note a process node makes money for a long, long while even when the cutting edge companies have left: https://images.anandtech.com/doci/13873/TSMC%20Tech.png half of the revenue is from 28nm and larger -- 28nm (which is another half node) was introduced Q4 2011. So it's possible without Apple they could've done it but it would've required a much bigger debt load.