E-learning is a learning environment which uses information and communication technologies (ICT's) as a platform for teaching and learning activities. It has been defined as "pedagogy empowered by technology", though 'digital technology' is more accurate. Note that, due to the difference in terms of institutional goals, higher education and the industry have very different ideas about what e-learning is and how e-learning can be/should be used.
E-learning has its root in distance learning and is part of the revolution brought by the new media: the Web. Educators and trainers soon found the potentials to advance learning at the advent of the new Web technologies. The advocates of e-learning voice for the breakdown of barriers to learning (especially for adult learners in higher education) such as the limitations in time and distance. Research on media comparison "proves" that there is no difference in the learning outcome of e-learning from traditional face-to-face instruction. Over time, more and more instructors/institutions are incorporating e-learning components in the practice of instruction in higher education as a way of facilitating learning.
See also 
- Wikipedia: E-Learning