For instance if you wanted to use the redis-fast-driver in NPM, in the past you might'e spun up a docker container and built it there or spun up a Linux vm and built it there. This is where the OPS cross-build environment capability comes into play. It spins up a small linux vm, executes your build instructions and then allows you to spit out the artifacts to your host system (MacOS in this case). This allows you to build native add-ons without resorting to a full-blown Linux vm or docker (which runs inside of a linux vm regardless).