What does TIER 1/1 Router mean

[jaadam1977]

I'm working on a network and I keep hearing about the TIER 1/1, TIER 0, and TIER 1/2 routers but I have no idea what any of this means. I have my CCNA and don't remember seeing any of this. Am I missing something?

Thanks for any help.

[Konstantin Dunaev]

I think TIER0 doesn't exists yet

but TIER1 TIER2 TIER3  are common classification of ISP, and some hardware supplier uses those names just to say that thier hardware can be as router on a TIer1 - Tier1  connection or Tier1-Tier2 connections.  But I'm not 100% sure.