A person listening to a standard stereo is hearing a multi-channel recording which is created (ideally) by placing two different microphones in a recording area to replicate two human ears. This is a decent form of recording for music in particular, as the concert experience tends to focus on facing towards on specific area in a large venue. For movies, however, stereo sound cannot suspend disbelief and trick the audience into feeling the sounds are real. In life, after all, sounds come from all directions. Stereo sound is flat and vague in comparison.
As one might expect, recording surround sound is simply an extension of the stereo concept. Rather than trying to replicate human ears, however, special surround sound recording equipment is used to record a full range of sounds coming from numerous different areas. This is an effective method recording for certain kinds of music such as symphonies taking place in a concert hall. In such a venue the acoustics of the concert hall are extremely important, and recreating the experience requires the ability to record more than the sounds coming straight from the stage. Of course, in today's age of digital media, the idea of recording a movie and presenting it in surround sound by simply using some sort of specialized microphone is fairly quaint. This is particularly true in films that use a lot of CGI or animated elements. There is, of course, no Optimus Prime and so no Optimus Prime sounds to record.
In either the case of a surround sound recorded using a special microphone or fabricated in a sound studio, all surround sound is delivered through the use of channels. Each channel consists of audio that can be mapped to a specific speaker or set of speakers. A stereo set up is usually two-channel because each speaker can deliver different sound than the other. A 5.1 channel system has left and right speakers in the front and rear and one center front speaker. The .1 stands for the Low Frequency Effects channel, a channel which is developed to deal with sub-bass effects. This channel is not dedicated to any particular speaker.