It's analogous to a release candidate in software. Basically means the fab line has passed all tests and run some test chips but hasn't actually done a producti

It's analogous to a release candidate in software. Basically means the fab line has passed all tests and run some test chips but hasn't actually done a production run of anything yet. The risk of issues / bad yield is higher than it would be after a few million chips have been run through the fab to work out all the kinks. In practical terms it means they aren't building low cost consumer products yet, they are probably building low volume high $ parts that desperately need 5nm. They are also probably doing a bunch of IP verification runs, confirming process designs for all the building blocks that are used to build SoCs: ARM cores, memory controllers, IO controllers, etc.