The Triple Data Encryption Algorithm, called 3DES for short, is an encryption algorithm that evolved from previous flavors of the same algorithm (Data Encryption Standard, or DES, which was first published in 1975). Although under certain configurations 3DES can be acceptable, it is being phased out slowly as there are new vulnerabilities that make the protocol significantly weaker. Where possible, newer standards such as AES should be used; there are no reasons to stick to 3DES apart from backward compatibility or legacy support.
For more details check the FAQ for this algorithm.