.tel is a new top-level domain approved by ICANN as a sponsored TLD launching on Wednesday, December 3, 2008 to trademark owners of national effect and on February 3, 2009 to anyone who wishes to apply. Its main purpose is as a single management and publishing point for “internet communication” services, providing a global contacts directory service by housing all types of contact information directly in the DNS. It is sponsored by Telnic Limited. In May 2006, it was approved to be added to the DNS root zone by ICANN. The TLD was added to the DNS root zone on March 2, 2007.
Since some of the sorts of services that will use .tel domains can be achieved on mobile telephones, there may be a perceived overlap in the target market between this and the .mobi domain, also approved by ICANN in the same round. However this perception is incorrect. In simple terms, .tel is about publishing contact data: phone numbers, SIP addresses and so on directly in the DNS, not on html-based websites. The focus of the .mobi domain is providing web sites and other content designed for the user interface provided on mobile phones and other hand-held devices.
For more details, refer this article.