Symmetric key algorithms are a type of encryption method where the same key is used for both encrypting and decrypting data. This means that both the sender and the receiver must have access to the same secret key to communicate securely. Because of this shared key, symmetric key algorithms are generally faster and more efficient than other types of encryption. However, the main challenge with symmetric key algorithms is securely sharing the key between parties. If someone else gains access to the key, they can easily decrypt the information. Common examples of symmetric key algorithms include AES (Advanced Encryption Standard) and DES (Data Encryption Standard).