What do parallel and serial mean respectively?

The above answers are all about data transmission. In fact, the concepts of parallel and serial are very broad: 1. In terms of data transmission, it is the problem of simultaneous transmission or unit transmission of multi-bit data. We can't say which is faster, mainly depending on the clock, transmission distance, physical medium, voltage form (if it is an electrical signal) and so on. If the above conditions are the same, parallel transmission will be faster, but it will increase the complexity and will be adopted by large computers or communication equipment. General personal computers, mobile phones and other communication equipment will use more convenient transmission. 2. In computing, it means that the computer executes instructions at the same time. Supercomputers and mainframes generally calculate in parallel, while personal computers do the opposite. Parallel computing is much faster, but its complexity is also high. In short, under the same conditions, parallel has advantages in speed, and serial has advantages in cost and convenience. Now the serial port transmission speed that everyone says is too expensive and inconvenient.