From http://www.ietf.org/ :

The InternetEngineeringTaskForce (IETF) is a loosely self-organized group of people who make technical and other contributions to the engineering and evolution of the Internet and its technologies. It is the principal body engaged in the development of new Internet standard specifications. Its mission includes:

	* Identifying, and proposing solutions to, pressing operational and technical problems in the Internet; 
	* Specifying the development or usage of protocols and the near-term architecture to solve such technical problems for the Internet; 
	* Making recommendations to the Internet Engineering Steering Group (IESG) regarding the standardization of protocols and protocol usage in the Internet; 
	* Facilitating technology transfer from the Internet Research Task Force (IRTF) to the wider Internet community; and 
	* Providing a forum for the exchange of information within the Internet community between vendors, users, researchers, agency contractors and network managers. 

The IETF meeting is not a conference, although there are technical presentations. The IETF is not a traditional standards organization, although many specifications are produced that become standards. The IETF is made up of volunteers who meet three times a year to fulfill the IETF mission. 

There is no membership in the IETF. Anyone may register for and attend any meeting. The closest thing there is to being an IETF member is being on the IETF or WorkingGroup mailing lists.