How Do Print Server Adapters Work with Modern Printers?

I'm trying to set up a small office network and heard about Print server adapters to connect multiple printers. Can someone explain how these work? Do they help older printers connect to the network? Also, do they improve printing speed or just manage connections? Are there any compatibility issues with newer models? If you've used one, what are the pros and cons? Any recommended brands or models to look out for?