So I finally saw a porcelain fused to metal crown in the wild today. It had a metal band that was visible even on the facial side, maybe 1mm or 1.5mm (not so good with metric yet), which compares to pictures I've seen on the internet. I also learned in class that some PFM crowns have a metal occlusal and lingual, but porcelain on the facial side.

I tried to google different styles of PFM crowns but I am getting images of what look like (to me, being not educated enough) ceramic crowns.

This is another one of those things that I don't know enough about to even google properly to find what I'm looking for. What search terms can I use to find out more? I have PFM crowns but there is no visible metal band on any surface, and I'd like to know more about them. I also would like to learn about why each type is used in which circumstances.

Yes this is out of my league but I'm curious anyways, so any google help would be appreciated :) Thanks!