This is pattern marking/tracing.
In particular a Japanese pattern.
I don't enjoy tracing Japanese patterns solely for the fact that I find it hard to actually find the right piece to be traced and my tracing looks like my 3.5yr old did it.
But this time around I used a ruler, some extra wide Glad Baking Paper and traced a pattern for a singlet top for myself.
It's also useful to copy the actual Japanese markings so you can recognise the symbols on the instructions. Above is the pattern piece for pages 14, 31 and labelled 'front' piece.
I hope to finish it soon. Not tonight, I have to shop but maybe by Sunday.