what is the purpose of RX and TX pins on the bolt?
It is used for UART communication. Check https://docs.boltiot.com/docs/serial-begin
RX is for the receiving signal
TX is for the transmitting signals
in the bolt wifi module rx and tx is for communication purpose
and it transmit datas between wifi module to bolt iot cloud
Tx and Rx are receiving and transmission pin that is used for UART protocol used for communication between any two devices and Tx of one device is connected to Rx of another and Rx of that one device to Tx of another.
This pins are used for UART/Serial Communication as said by @PPV.
Incase you want to connect Bolt module with any other Controller board say Arduino UNO, then you’ll have to connect the TX pin of Bolt module to RX pin of Controller board & the RX pin of Bolt module to TX pin of Controller.
Hope it helps.