If using the Uno as FTDI, like aarg says, the serial connection would be RX to RX, TX to TX.
If you could, please, tell us what you want to do with the ESP/Uno combination we could give more specific advice.
If using the Uno as FTDI, like aarg says, the serial connection would be RX to RX, TX to TX.
If you could, please, tell us what you want to do with the ESP/Uno combination we could give more specific advice.