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")
```

if (pwallet->HaveKey(keyid)) {
                    pwallet->WalletLogPrintf("Skipping import of %s (key already present)\n", EncodeDestination(keyid));
                    continue;
                }
                int64_t nTime = DecodeDumpTime(vstr[1]);
                std::string strLabel;
                bool fLabel = true;
                for (unsigned int nStr = 2; nStr < vstr.size(); nStr++) {
                    if (vstr[nStr].front() == '#')
                        break;
                    if (vstr[nStr] == "change=1")
                        fLabel = false;
                    if (vstr[nStr] == "reserve=1")
                        fLabel = false;
                    if (vstr[nStr].substr(0,6) == "label=") {
                        strLabel = DecodeDumpString(vstr[nStr].substr(6));
                        fLabel = true;
                    }
                }
                pwallet->WalletLogPrintf("Importing %s...\n", EncodeDestination(keyid));
                if (!pwallet->AddKeyPubKey(key, pubkey)) {
                    fGood = false;
                    continue;
                }
                pwallet->mapKeyMetadata[keyid].nCreateTime = nTime;
                if (fLabel)
                    pwallet->SetAddressBook(keyid, strLabel, "receive");
                nTimeBegin = std::min(nTimeBegin, nTime);
            } else if(IsHex(vstr[0])) {
               std::vector<unsigned char> vData(ParseHex(vstr[0]));