Ah, got it.
More often than not when someone is asking about a "public key" they are simply referring to a Bitcoin address. The question comes up because most ledger systems require an "account number" or similar to be created in advance before transactions related to that entity can occur. So the question comes up from people wanting to know where each and every bitcoin address that exists is stored. And the answer to that question, of course, is that bitcoin doesn't require an address to be known by the nodes of the network before it is used. So addresses exist without the rest of the network knowing about them. (e.g,, by default 100 addresses are in each node's keypool which the rest of the network does not know anything about.)