XML ( http://en.wikipedia.org/wiki/XML ), is an important format of information that allows businesses from around the world and in different industries and different computing systems to communicate and do business electronically and automatically in many ways. XML is already a major part of many of the technologies you use from several websites, to desktop applications, to business apps and more and usually works behind the scene thus taking the complexity away from the user and giving them a transparent easy experience.
XML is definitely the future and is important to take note of as it allows big business and innovation to happen much quicker due to its very open nature. It is free to use by anybody although there are licenses around certain use cases and software packages that use this technology, its underlying foundation is free. For the Global Good of the world we are going to need a lot more technological innovation so read up on XML and start innovating!