Answer

Hamming code is an error-detecting and error-correcting block code that adds parity bits to data so that certain bit errors can be detected and corrected at the receiver.

For a data word containing $m$ data bits, the number of parity bits $r$ is chosen so that:
$2^r \ge m+r+1$.

The parity bits are placed at positions that are powers of 2: $1,2,4,8,\ldots$. Their parity checks allow the receiver to determine the position of a single-bit error.

Exam-ready answer

Hamming code is a forward error-correction technique that adds redundant parity bits to a data word. It can generally correct a single-bit error and detect certain multiple-bit errors depending on the variant.

For 2 marks: Definition + single-bit error-correction property is sufficient.