The Pattern on the Stone by Daniel Hillis JUL 18 2002
A one-paragraph explanation of how a computer works from Danny Hillis's The Pattern on the Stone (which you should read if you're interested in how computers work but don't really know):
"The work performed by the computer is specified by a program, which is written in a programming language. This language is converted to sequences of machine-language instructions by interpreters or compilers, via a predefined set of subroutines called the operating system. The instructions, which are stored in the memory of the computer, define the operations to be performed on data, which are also stored in the computer's memory. A finite-state machine fetches and executes these instructions. The instructions as well as the data are represented by patterns of bits. Both the finite-state machine and the memory are built of storage registers and Boolean logic blocks, and the latter are based on simple logical functions, such as And, Or, and Invert. These logical functions are implemented by switches, which are set up either in series or in parallel, and these switches control a physical substance, such as water or electricity, which is used to send one of two possible signals from one switch to another: 1 or 0. This is the hierarchy of abstraction that makes computers work."
Reading Hillis's explanation reminds me of Ray and Charles Eames's classic Powers of Ten film. In the same way that the computer is able to function by abstracting levels of functionality, expanding or limiting our view of the universe helps us understand it better, dealing with it at different scales rather than all at once (you don't get very far in describing the our solar system in terms of individual subatomic particles).