This RS232 to TTL Serial Interface Module is a board with the MAX3232 transceiver integrated circuit (IC). It facilitates serial communication between TTL and RS232 ports by providing the necessary electrical signal conversion.
 
These boards usually have a DB9 connector soldered at one end, and four header pins with jumper cables at the other end. The jumper cables enable the user to connect the wires to a breadboard or a microcontroller project board, whilst the DB9 connects directly to a COM port of a computer.