The linear communication model is a basic representation of how people communicate with each other. It involves two people, the sender and the receiver. The sender conveys a piece of information, called the "message" to the receiver by any channel of communication. Different channels of communication are email, face-to-face, and over the phone. Every channel of communication is susceptible to a different kind of "noise", or distraction, such as a pop-up add, or poor cell-phone reception. The noise is not necessarily auditory, it is anything that reduces the clarity of the message.
This model can be applied to many situations, but it is most accurately applied to online communication. The main reason is that channels of communication like email do not allow for immediate feedback.
Example: You, the sender, send an email, the channel of communication, about earning extra credit, the message, to your teacher, the recipient. Your poor grammar, noise, makes it harder for your teacher to understand your message.