True Type vs. Open Type

Question

What is the difference between true type and open type font? Does the latter suggest openness as in open-source? Does the OS use a different "engine" for rendering those two?

Edit: Sorry, wasn't really clear in my original question. I was actually looking for more explanation regarding the visual difference (if any) between the two; maybe one has more limitation in the e.g. angles to generate curves, etc.

Answer 1

The two may use different technologies for describing character outlines. There is no relationship with open source.

TrueType fonts use TrueType outline descriptions, OpenType fonts may use either TrueType outlines or CFF (Compact Font Format) outlines.

Specifications for both formats are published and freely available.

Answer 2

A simple wikipedia/google search would get you to....

OpenType is a format for scalable computer fonts. It was built on its predecessor TrueType, retaining TrueType's basic structure and adding many intricate data structures for prescribing typographic behavior. OpenType is a registered trademark of Microsoft Corporation.[2] The specification germinated at Microsoft, with Adobe Systems also contributing by the time of the public announcement in 1996. The specification continues to be developed actively and is presently migrating to an open format. Because of wide availability and typographic flexibility, including provisions for handling the diverse behaviors of all the world's writing systems, OpenType fonts are used commonly today on the major computer platforms.