From the NIST press release:
Hash algorithms are used widely for cryptographic applications that ensure the authenticity of digital documents, such as digital signatures and message authentication codes. These algorithms take an electronic file and generate a short "digest," a sort of digital fingerprint of the content. A good hash algorithm has a few vital characteristics. Any change in the original message, however small, must cause a change in the digest, and for any given file and digest, it must be infeasible for a forger to create a different file with the same digest.Apparently Keccak performs better in hardware applications, so it may be an alternative to secure communications in mobile devices. Keccak also doesn't have the same vulnerabilities SHA-2 has been accused of.
Bruce Schneier has a great post on the topic: http://www.schneier.com/blog/archives/2012/10/keccak_is_sha-3.html