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")
```

{
    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() > 0)
        throw std::runtime_error(
            "abortrescan\n"
            "\nStops current wallet rescan triggered by an RPC call, e.g. by an importprivkey call.\n"
            "\nExamples:\n"
            "\nImport a private key\n"
            + HelpExampleCli("importprivkey", "\"mykey\"") +
            "\nAbort the running wallet rescan\n"
            + HelpExampleCli("abortrescan", "") +
            "\nAs a JSON-RPC call\n"
            + HelpExampleRpc("abortrescan", "")
        );
    if (!pwallet->IsScanning() || pwallet->IsAbortingRescan()) return false;
    pwallet->AbortRescan();
    return true;
}
static void ImportAddress(CWallet*, const CTxDestination& dest, const std::string& strLabel);
static void ImportScript(CWallet* const pwallet, const CScript& script, const std::string& strLabel, bool isRedeemScript) EXCLUSIVE_LOCKS_REQUIRED(pwallet->cs_wallet)