Physically, yes you can connect a U-Verse receiver to a playstation 3 via HDMI, but it wouldn't work.

If you're trying to get your PS3 onto the internet, if your U-Verse receiver's is connected to your gateway via coax, you should be able to use the Ethernet port on the back of it and connect it to your playstation to get internet access on the playstation.

The STB acronym is short for Set Top Box, also known as your U-Verse receiver. As for tags, they're someone a few users add to posts to help people find certain topics when searching the board. Personally, I don't use them but I see the usefulness for those who do use them.