Specifically, it adds an address into the wallet.

Easy to test now thanks to https://github.com/bitcoin/bitcoin/pull/14410
```
diff --git a/test/functional/wallet_importmulti.py b/test/functional/wallet_importmulti.py
index 9ba6860..bff37b2 100755
--- a/test/functional/wallet_importmulti.py
+++ b/test/functional/wallet_importmulti.py
@@ -95,6 +95,7 @@ class ImportMultiTest(BitcoinTestFramework):
         assert_equal(address_assert['iswatchonly'], True)
         assert_equal(address_assert['ismine'], False)
         assert_equal(address_assert['timestamp'], timestamp)
+        assert_equal(address_assert['ischange'], True)
 
         # ScriptPubKey + internal + label
         self.log.info("Should not allow a label to be specified when internal is true")
```

LOCK2(cs_main, pwallet->cs_wallet);
    EnsureWalletIsUnlocked(pwallet);
    std::string strAddress = request.params[0].get_str();
    CTxDestination dest = DecodeDestination(strAddress);
    if (!IsValidDestination(dest)) {
        throw JSONRPCError(RPC_INVALID_ADDRESS_OR_KEY, "Invalid Bitcoin address");
    }
    auto keyid = GetKeyForDestination(*pwallet, dest);
    if (keyid.IsNull()) {
        throw JSONRPCError(RPC_TYPE_ERROR, "Address does not refer to a key");
    }
    CKey vchSecret;
    if (!pwallet->GetKey(keyid, vchSecret)) {
        throw JSONRPCError(RPC_WALLET_ERROR, "Private key for address " + strAddress + " is not known");
    }
    return EncodeSecret(vchSecret);
}
UniValue dumpwallet(const JSONRPCRequest& request)
{
    std::shared_ptr<CWallet> const wallet = GetWalletForJSONRPCRequest(request);
    CWallet* const pwallet = wallet.get();
    if (!EnsureWalletIsAvailable(pwallet, request.fHelp)) {
        return NullUniValue;
    }
    if (request.fHelp || request.params.size() != 1)
        throw std::runtime_error(
            "dumpwallet \"filename\"\n"
            "\nDumps all wallet keys in a human-readable format to a server-side file. This does not allow overwriting existing files.\n"
            "Imported scripts are included in the dumpfile, but corresponding BIP173 addresses, etc. may not be added automatically by importwallet.\n"
            "Note that if your wallet contains keys which are not derived from your HD seed (e.g. imported keys), these are not covered by\n"