The two most popular kinds of plastic are currently used for keyboards are:
ABS (acrylonitrile butadiene styrene) - the most common keycap plastic used, tends to feel smooth, is durable, a tad cheaper and easier to manufacture than PBT
PBT (polybutylene terephthalate) - tends to have a “matte” texture, a bit stiffer than ABS, a bit more durable than ABS, and doesn’t develop a “glossy” look with use over time like ABS, harder and more expensive to manufacture than ABS
Sublimated dying infuses the ink with the plastic through a manufacturing process Elder Sage perfectly describes:
https://drop.com/talk/27150/what-does-it-mean-that-these-are-dye-sublimted-pbt/2582700
The ink sinks into the keycap just a bit so the font doesn't wear out even if the keycap gets worn down.
Hence “Dye-Subbed PBT”.
EyalRoI'll second the second. After about a month of using the keys, I think my biggest source of typos is still from (occasionally) having my home row fingers off by one key. I wouldn't go back, though. The deep homing dishes feel so nice on the fingers.