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TrueType is an outline font standard originally developed by Apple Computer in the late 1980s as a competitor to Adobe's Type 1 fonts used in PostScript. The primary strength of TrueType was originally that it offered font developers a high degree of control over precisely how their fonts are displayed, right down to particular pixels, at various font heights.
In, 1991 Microsoft added TrueType into the Windows 3.1 operating system. In partnership with their contractors, Monotype Corporation, Microsoft spent much effort creating a set of high quality TrueType fonts that were compatible with the core fonts being bundled with PostScript equipment at the time. This included the fonts that are standard with Windows to this day: Times New Roman (compatible with Times Roman), Arial (compatible with Helvetica) and Courier New (compatible with Courier). One should understand "compatible" to mean two things: first, that the fonts are similar to look at, and second, very importantly, the fonts have the same character widths so can be used to typeset the same documents without reflowing the text. (The disjunction of the names, particularly between Arial and Helvetica, led some to believe there was a general problem of having to determine an "equivalent" Apple or PostScript font whenever a particular Windows font was called for, or vice versa. However, while the character outlines themselves are different, the styles and weights have been made similar enough that the average user is unable to tell the fonts apart.)
Microsoft and Monotype technicians used TrueType's hinting technology to ensure that these fonts did not suffer from the problem of illegibility at low resolutions which had previously forced the use of bitmapped fonts for screen display. Subsequent advances in technology have introduced first anti-aliasing, which smooths the edges of fonts at the expense of a slight blurring, and more recently subpixel rendering (the Microsoft implementation goes by the name ClearType), which exploits the pixel structure of TFT LCD based displays to increase the apparent resolution of text. Microsoft has marketed these technologies particularly heavily, and they are now widely used on all platforms.
TrueType has long been the most common format for fonts on Mac OS and Windows, although both also include native support for Adobe's Type 1 format and the OpenType extension to TrueType (since Mac OS X 10.0 and Windows 2000). While some fonts provided with the new operating systems are now in the OpenType format, most free or inexpensive third-party fonts use plain TrueType.
Increasing resolutions and new approaches to screen rendering have reduced the requirement of extensive TrueType hinting. Apple's rendering approach on Mac OS X ignores almost all the hints in a TrueType font, while Microsoft's ClearType ignores many hints, and according to Microsoft, works best with "lightly hinted" fonts.
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