What is EDE (Encrypt-Decrypt-Encrypt)?

Triple DES works in three stages and is known as Encrypt-Decrypt-Encrypt (EDE). It operates by taking three 56-bit keys that are K1, K2 and K3, and encrypting first with K1, decrypting next with K2 and encrypting a last time with K3. 3DES has two-key and three-key forms.