Error control coding (Source/Channel coding) involves adding extra 'redundant' bits to the actual data bits before transmission. These extra bits follow specific mathematical rules related to the data bits. At the receiver, these rules are checked. If a discrepancy is found, it indicates an error. Depending on the code used (e.g., Hamming code, Reed-Solomon), the receiver can not only detect that an error occurred but also correct it by determining which bit was flipped.