OpenType is a cross-platform font format which supports large character sets and complex typographic features.

PostScript Type 1 fonts
How to choose different styles of numerals in applications which support advanced OpenType typographic layout features.
Activating Small Caps in OpenType fonts
The difference between Typotheque's OpenType Std and Pro fonts is that Std fonts do not include Cyrillic and Greek characters. All other features in these fonts are identical.
Comprehensive table of OpenType feature tags and their support in applications (software). OpenType features are created by using the tags in creating feature scripts that describe how characters are to be manipulated to make the desired feature.
Typotheque offers Multilingual Unicode Compliant Fonts in WGL4, and larger character sset supporting over 80 languages in standard Latin, Central European, Baltic, Turkish, Greek, Cyrillic, and Arabic encodings.