Complex sentence: Most modes require a unique binary sequence, often called an initialization vector (IV), for each encryption operation to produce distinct ciphertexts when the same plaintext is transformed multiple times independently with the same key.
Split into simpler sentences: Most modes require a unique binary sequence for each encryption operation, often called an initialization vector (IV). The initialization vector is used to ensure distinct ciphertexts are produced even when the same plaintext is transformed multiple times independently with the same key.