Define baud rate

The rate of data transfer in serial data communication is signified in bps. Bits per second (bps) is the rate of transfer of information bits. Baud is the number of signal level changes per second in a line, irrespective of the information content of those signals. Baud and bps rates aren't necessarily equal. Ratio of BPS to baud depends on information-coding scheme that you are using. For instance each character in asynchronous RS-232 coding includes a start and stop bit that aren't counted as information bits so BPS rate is actually less than baud rate.