What's the difference between block ciphers and symmetric-key encryption? Both block ciphers and symmetric-key encryption use a secret key to transform plaintext into ciphertext, and do so in a reversible manner. Are they the same? Or does symmetric-key encryption also includes things other than block ciphers?
Symmetric-key scheme just means use a key to encrypt and decrypt the same message.

Block ciphers just means encrypt your data in many small bits blocks (which can vary in size with padding randomized technique).