The former is the receive data line used to receive serial data while the latter is the transmission line used to transmit serial data.
If you haven't already, check out the documentation on the Pico.
It is the Slave Select line, which is used by the master.
Provide the power and attach the necessary peripherals.
Products you might be interested with: This is what Im getting….
Arduino is an open-source platform provided by Arduino.
Description: But that port is only visible when the board is in bootloader mode, so pull the reset line low twice quickly to invoke the bootloader reset feature discussed above.