user51018: Do they have specific pins that is best to be use as Rx/Tx pins (aside from D0 and D1)? If so, what makes them special?
edit: What pin feature i should look out for when choosing the rx/tx pin? Is there any specific pins that will make it a better rx/tx pin?

user37622: The Arduino SoftwareSerial library can use any pair of pins. 
AltSoftSerial uses special pins. AltSoftSerial uses a 16 bit hardware timer to generate the transmit output and measure the receive input waveforms. The timer works on pins 8 and 9 on Uno and Atmega 328p boards.

user6936: Pins D0 and D1 are used for hardware serial, see Serial library reference.
You can use any other pins for virtual Rx/Tx lines employing a software serial mode, for example by using the SoftwareSerial library, see Software Serial example, or by implementing your own custom code, or custom library.

51018: <p>Do they have specific pins that is best to be use as Rx/Tx pins (aside from D0 and D1)? If so, what makes them special?</p>

<p>edit: What pin feature i should look out for when choosing the rx/tx pin? Is there any specific pins that will make it a better rx/tx pin?</p>
 37622: <p>The Arduino SoftwareSerial library can use any pair of pins. </p>

<p><a href="https://www.pjrc.com/teensy/td_libs_AltSoftSerial.html" rel="nofollow noreferrer">AltSoftSerial</a> uses special pins. AltSoftSerial uses a 16 bit hardware timer to generate the transmit output and measure the receive input waveforms. The timer works on pins 8 and 9 on Uno and Atmega 328p boards.</p>
 6936: <p>Pins <code>D0</code> and <code>D1</code> are used for <em>hardware serial</em>, see <a href="https://www.arduino.cc/reference/en/language/functions/communication/serial/" rel="nofollow noreferrer"><code>Serial</code></a> library reference.</p>

<p>You can use any other pins for virtual Rx/Tx lines employing a <em>software serial</em> mode, for example by using the <code>SoftwareSerial</code> library, see <a href="https://www.arduino.cc/en/Tutorial/SoftwareSerialExample" rel="nofollow noreferrer">Software Serial example</a>, or by implementing your own custom code, or custom library.</p>
