Linear block codes encode messages by adding parity bits to create codewords. They have the following properties: 1) They encode a k-bit message into an n-bit codeword, where n-k bits are parity bits calculated from the message bits. 2) Syndrome decoding uses the parity check matrix H to detect and locate errors by calculating the syndrome s, which depends only on the error pattern. 3) A linear block code can correct up to t errors per codeword if the minimum distance dmin is greater than 2t+1.