FTDI USB/TTL-serial converter - what are TXD, TXL, RXD and RXL?
If the SparkFun FT232RL Breakout is anything to go by, then the TXD and RXD pins are physically connected to the TX and RX pins. This is because the breakout board can support two configurations, then 6-pin edge connector, and the full 18-pin PCB arrangement.

The TXL and RXL are likely status LED pins used to indicate when a TX packet is being sent and an RX packet being received respectively. Sparkfun calls them TXLED and RXLED respectively, which have the same pin locations as the clone boards that call them TXL/RXL.



In summary:


TXD = TX = Transmit
RXD = RX = Receive
TXL = TX LED = Transmit In Progress LED
RXL = RX LED = Receive In Progress LED