Balanced means that the audio signal is going evenly to each channel. (Left and Right)
Unbalanced means that the audio signal is going unevenly to channel. Balanced audio means that neither signal carrying wire is used for the ground. The ground is a separate conductor. Most of these audio cables have 3 wires inside. Unbalanced means that one of the signal carrying wires is also is used for ground thus a 2 wire cable.

There are speaker cables, unbalanced analog cables, balanced analog cables, coaxial digital audio cables and optical audio cables.

depends on the connection that each end has, but usually it is balanced 1/8" plug to balanced 1/8" plug. A better solution would be to put the CD on the CD-drive of the computer.

A balanced mic is based on a balanced connection offering better rejection to outside noise by a phenomenon known as CMR, common mode rejection. For example, audio is AC at any moment at any single place on a twisted pair balanced cable, the audio is both +5 and - 5 V. If external noise is inducted on to the cable at, say +1 V, that +1 V is added to the + 5 and the - 5. As an arithmetic trick of elementary electronics, the noise is cancelled out inside the circuitry of the next stag In other words, a balanced mic helps to elimate noise balancing the audio output. Unbalanced means it has less power, meaning it may produce more erroneous noise. http://forums.creativecow.net/readpost/30/857322

A good balanced audio output with a good quality low loss cable and a true balanced receiver allows audio to be run for distances running into thousands of feet.

One of the most challenging cable runs for outside broadcasts is at golf tournaments. Audio signals from microphones back to the production truck can approach a mile in length. There are certainly some loss of signal levels at that length but with robust, high quality cable, clean signals are delivered and used without problem.

It seems unlikely that a home theater application will come close to those cable runs unless you have a very, very big theater.