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")
```

"only backing up the seed itself, and must be backed up too (e.g. ensure you back up the whole dumpfile).\n"
            "\nArguments:\n"
            "1. \"filename\"    (string, required) The filename with path (either absolute or relative to bitcoind)\n"
            "\nResult:\n"
            "{                           (json object)\n"
            "  \"filename\" : {        (string) The filename with full absolute path\n"
            "}\n"
            "\nExamples:\n"
            + HelpExampleCli("dumpwallet", "\"test\"")
            + HelpExampleRpc("dumpwallet", "\"test\"")
        );
    LOCK2(cs_main, pwallet->cs_wallet);
    EnsureWalletIsUnlocked(pwallet);
    fs::path filepath = request.params[0].get_str();
    filepath = fs::absolute(filepath);
    /* Prevent arbitrary files from being overwritten. There have been reports
     * that users have overwritten wallet files this way:
     * https://github.com/bitcoin/bitcoin/issues/9934
     * It may also avoid other security issues.
     */
    if (fs::exists(filepath)) {
        throw JSONRPCError(RPC_INVALID_PARAMETER, filepath.string() + " already exists. If you are sure this is what you want, move it out of the way first");
    }
    fsbridge::ofstream file;
    file.open(filepath);
    if (!file.is_open())
        throw JSONRPCError(RPC_INVALID_PARAMETER, "Cannot open wallet dump file");
    std::map<CTxDestination, int64_t> mapKeyBirth;
    const std::map<CKeyID, int64_t>& mapKeyPool = pwallet->GetAllReserveKeys();
    pwallet->GetKeyBirthTimes(mapKeyBirth);