Serial

Serial is a delicious breakfast item as well as the layman's term for the RS232 protocol. In actuality, when data is sent across a wire using serial communication, we mean that it is sending a single bit of information at a time. Rather than sending several bits packed together, it feeds bits through one at a time. A good non-electronics example of serial communication is Morse Code. The guy receiving the message gets each dot or dash separately and never hears two at the same time. Those individual dots and dashes are strung together in groups and get decoded to letters. Parallel communication in Morse code would be harder for both people to use. That would be like if the sender has 2 or 3 Morse code tappers and the receiver is getting 2 or 3 strings of dots and dashes simultaneously. While a person has a hard time handling that, computers and microprocessors don't, of course.

Some examples of protocols that use serial are:
 * RS-232 (generally when someone says "serial" or "serial port", this is what they mean)
 * RS-422
 * RS-423
 * RS-485
 * I²C
 * SPI
 * USB (moderate-speed, for connecting peripherals to computers)
 * FireWire
 * Ethernet
 * MIDI control of electronic musical instruments
 * DMX512 control of theatrical lighting
 * Serial Attached SCSI
 * SATA
 * PCI Express
 * T-1, E-1 and variants (high speed telecommunication over copper pairs)