I read that the R56 models have composite camshafts.
What exactly does this mean?

 

Never mind. I found this:

The camshafts on both engines are composite structures, meaning that cam
rings made of high-strength stainless steel are shrunk on to a cast shaft and
subsequently machined. In the final fine-polishing process the cams are then
machined to an accuracy of 1 micron (1⁄1,000 mm). For reasons of weight
the eccentric shaft is also made in this process for the first time, likewise with tolerance levels in the micron range.