It segments a certain amount of ram to “swap” to which means compress and store. Normal blue sky ram operations are not compressed on macOS
Many operations are actually a lot faster with compressed memory than without. It's all about where the bottleneck is.
Oh, yes compressed swap makes much more sense, thanks.
It is not compressed swap, the compressed data is still in RAM. The OS just compresses inactive memory, with a couple of criteria to define “inactive”.