It's Authentication/Identity. But really it's a federated system of consent where you can allow one authoritative holder of some information about you to transmit it to another. Simple E.g. omitting many details but say some federal government agency (A) wants my driver's licence number. because I use the same identity for both (A) and my state department of transport (B) I can tell (B) it's ok to send it to (A). (A) and (B) are both in the "network" which is governed by a central Register (R) and verifies each to each other so they can securely share data over standardized channels. The central register does not get involved beyond legitimising (A) and (B) to each other. The benefit is for a lot of cases the specific information stays with the relevant party, you just consent to when one needs to borrow some from another.
It’s not going into granularity you may want though.
For context, here in NL we’ve had such a system for some time (“DigID”) and as a citizen I find it infinitely better than the mess we had before. I don’t think that it gives government agencies access to information about me that they didn’t already have.