Parallel parity is based on regular parity. Parallel parity can detect weather or not there was an error, furthermore it can detect which bit has flipped. This method is implemented on a block of data which is made of sum words, the parity bit is then added to the columns and rows. Following an example:
As we can see in the example above, every row has its parity bit, and every column has its parity bit. If one bit in the block has flipped, we get two parity errors, one in the row's parity and one in the column's parity, by intercepting the row and column we can detect the bit that has flipped.