A typewriter has a keyboard, with keys for the characters in its font. The method by which the typewriter actually marks the paper now varies as greatly as types of printers do, but until the end of the 20th century was by the impact of a metal (or, later, metallized plastic) type element against an "inked" ribbon which caused ink to be deposited on the paper. Carbon paper was sometimes inserted between multiple pieces of paper, so the impact also caused duplicate characters to be printed on each layer of paper.
The typewriter was invented in 1867 by Christopher Sholes, Carlos Glidden, and Samuel W. Soule. The patent (US 79,265) was sold for $12,000 to a couple of entrepreneurs who made an agreement with E. Remington and Sons (then famous as a manufacturer of sewing machines), to commercialize what was known as the Sholes and Glidden Type-Writer. Remington started production of the first practical typewriter on March 1, 1873 in Ilion, New York.
In the original design style, now known as a "mechanical" or "manual" typewriter, each key was attached to a typebar that had the corresponding letter molded into its other end. When a key was struck briskly and firmly, the typebar hit a ribbon (usually made of inked fabric) stretched in front of a cylindrical platen that moved back and forth. The paper was rolled around by the typewriter's platen which was rotated by a lever (the "carriage return" lever at the far left) to each new line of text. Some typewriters used ribbons that were inked in black and red, each a stripe half the width and the entire length of the ribbon, and there was a lever to switch between them, for typing bookkeeping entries, where negative amounts had to be in red.
Electrical typewriter designs removed the direct mechanical connection between the keys and the element that struck the paper, and Remington's electric typewriters were the most common until IBM broke the mold with the IBM Selectric typewriter, which replaced the typebars with a spherical typeball (more correctly, "element"), slightly smaller than a golf ball, with the letters molded on its surface and a system of electric motors for rotating the ball into the correct position, then striking it against the ribbon, so the typeball moved across in front of the paper instead of the platen's carrying the paper across a stationary print position.
The typeball design had many advantages, especially elimination of "jamming" when more than one key was struck at once and the ability to change the typeball, thus allowing multiple fonts in one document. Selectrics were widely used as computer terminals in the 1970s, because the electronic instructions for manipulating the typeball could come just as easily from a computer as from the keyboard, and then the keyboard communicated to the computer, and the computer communicated to the typeball.
Later models of Selectrics replaced inked fabric ribbons with "carbon film" ribbons (that had a dry black (or, later, colored) powder on a ("once-thru") clear plastic tape and could be used only once but were in a cartridge that was easy to replace); introduced auto-correction (where a sticky tape in front of the print ribbon could remove the black-powdered image of a typed character); and introduced selectable "pitch" (so the typewriter could be switched among pica ("10 pitch"), elite ("12 pitch"), and sometimes agate ("15 pitch") even in one document). The final major development of the typewriter was "electronic" typewriters, most of which replaced the typeball with a daisy wheel mechanism (a disk with the letters molded on the outside edge of the "petals"). A plastic daisy-wheel was much simpler and cheaper than the typeball but frequently wore out and had to be replaced. Some electronic typewriters were basically dedicated word processors with internal memory and, often, cartridge or diskette external memory-storage devices.
In the developed world, with the proliferation of the personal computer, typewriters have faded into near-obscurity and are now used mainly by people without access to, or the training to use, a computer, and for specialized applications such as filling out forms. However they are still commonly used in poor countries which lack access to computers or to an electricity supply.
In some of those countries it is possible, in medium sized towns or large villages, to go to the public square and find individuals who gather there with their old but sturdy typewriters. These individuals rent out their services as letter writers, on the spot. They have illiterate or semi-literate customers who tell them what they want in their letters and they also have literate individuals who do not own a typewriter and wish to send a well done letter to an official or some other correspondent who would not be impressed by manuscript correspondence.
The 1874 Sholes & Glidden typewriters established the QWERTY layout for the letter keys that is used in virtually all computer and other keyboards nowadays. This layout of keys has been adopted as the de facto standard for English-language keyboards. Other nations using the Latin alphabet use variants of the QWERTY layouts, for example the French AZERTY layout.
Radically different layouts such as the Dvorak keyboard have been proposed but have not been able to displace the QWERTY layout, despite the advantages claimed by their proponents.