Symmetric Key Cryptography is a method of encryption where the same key is used for both encrypting and decrypting information. This means that both the sender and the receiver must possess the same secret key to communicate securely. The key must be kept confidential, as anyone with access to it can read the encrypted messages. This type of cryptography is efficient and fast, making it suitable for encrypting large amounts of data. However, the challenge lies in securely sharing the key between parties, as any compromise can lead to unauthorized access to the information being protected.