The transmission of information, via a medium and a code, and it's succussful (accurate) reception. See signal. In human language, the information is an idea, symbolized by a sentence. The meaning is the information, the language is the code, and the medium is sound waves, or printed letters. Successful reception is hard to measure, but is done constantly. In comuters, the information is data, the code is the protocol, and the medium is a digital signal. Successful reception is easy to measure. Sophisticated error-checking has developed over the years, and compression schemes have made it possible to put far more information on one phone line than previously thought possible. Though phone lines can only reliably transmit a signal of 9.6K, speeds 10x higher are possible by using mutiple 'tones,' set at frequencies calculated to avoid interference. Technically, almost everything a computer does is commuication. From the CPU to the RAM, then to the hard disk, every time data moves, it has a meaning, uses a medium, and the meaning is encoded in binary.