A typewriter is a mechanical
A machine manages power to accomplish a task, examples include, a mechanical system, a computing system, an electronic system, and a molecular machine. In common usage, the meaning is that of a device having parts that perform or assist in performing any type of work...

 or electromechanical device with keys that, when pressed, cause characters
In typography, a typeface is the artistic representation or interpretation of characters; it is the way the type looks. Each type is designed and there are thousands of different typefaces in existence, with new ones being developed constantly....

 to be printed on a medium, usually paper
Paper is a thin material mainly used for writing upon, printing upon, drawing or for packaging. It is produced by pressing together moist fibers, typically cellulose pulp derived from wood, rags or grasses, and drying them into flexible sheets....

. Typically one character is printed per keypress, and the machine prints the characters by making ink impressions of type elements similar to the pieces of cast metal type (called sorts)
Sort (typesetting)
In typesetting by hand compositing, a sort is a piece of type representing a particular letter or symbol, cast from a matrix mould and assembled with other sorts bearing additional letters into lines of type to make up a forme from which a page is printed.-See also:* History of western typography*...

 used in movable type
Movable type
Movable type is the system of printing and typography that uses movable components to reproduce the elements of a document ....

 letterpress printing
Letterpress printing
Letterpress printing is relief printing of text and image using a press with a "type-high bed" printing press and movable type, in which a reversed, raised surface is inked and then pressed into a sheet of paper to obtain a positive right-reading image...

. From their invention in 1868 through much of the 20th century, typewriters were indispensable tools for recording the written word.