Its part of a very silly kind of gamification here. Somewhere in the depth of the Welcome and HowTo section of this forum there should be a list explaining all those many stones.
PTC admins thought that a simple number like the 7 in your case is not enough to indicate the rank of a user (whatever rank should mean anyway). We also have a list of stones like your Bedrock or my Ruby and as if the huge list of 20-30 stones would not be enough, some of those stones even have kind of sub ranks (the roman numbers) like the V in my Ruby V. And, no, kids, thats not all - for users with reading disability there is also additionally a speedometer as a rank indicator.
I have never understood why we are treated like little kindergarten children in this respect 😞
To see if a user may have experience and you should rely on his answer you may also mouseover his username and you will see the number of postings he wrote, the number of kudos he got from other users and number of solutions he/she provided.
And, yes, you also see a lot of badges, the meaning of which has never been clear to me either, but somewhere there is surely also a list explaining them.
EDIT: Ah, I just see that @DJNewman found the stone list and posted the link to it,
