E-learning refers to the situation where the interaction between the students and the instructor is done online. Basically, the students receive the training and are taught through an online medium. The instructor is in constant contact with the student through synchronous and a-synchronous intervention tools. It simulate and intensify the authentic class learning situations.
B-learning is a combination of learning at a distance and the traditional on-site learning (in a class-room). Basically, students will have a (more or less) fixed schedule where they will have to attend a part of the classes at the educational institution and for the rest, they can make their own schedule, attend the rest of the classes and do their coursework and assignments online.
In online learning, the key element is the use of internet and is described as the learning experience that is realized with the use of technology learning tools. The student follows the course normally without an instructor intervention. All the necessary learning materials are online.