There is no Wiki about that and no post explaining
You can obtain some explanation from
bitcoind --help.
-walletnotify=<cmd>
Execute command when a wallet transaction changes. %s in cmd is replaced by TxID, %w is replaced by wallet name, %b is replaced by the hash of the block including the transaction (set to 'unconfirmed' if the transaction is not included) and %h is replaced by the block height (-1 if not included). %w is not currently implemented on windows. On systems where %w is supported, it should NOT be quoted because this would break shell escaping used to invoke the command.