Just go to Glyphs, on the font presentation page.
Briefly, OpenType is a font format jointly developed by Adobe and Microsoft in the late 1990ʼs. It came into wider use only after 2000, when Adobe included support for advanced typographic features in their InDesign, PhotoShop, and Illustrator applications.
We offer fonts primarily in OpenType format. OpenType is the only cross-platform format, i.e. the same file will work on both Macintosh and Windows computers.
If you only work with Latin-based languages (e.g. English, French, Polish, Czech or Turkish) then our OpenType Std fonts will meet your needs. If you also require support of Vietnamese, Russian or Greek, then you’ll need OpenType Pro fonts.
If you previously purchased a licence for an OpenType Std font (support for Latin-based languages only) and now need the OpenType Pro version (support also for Greek, Greek polytonic, Cyrillic and Vietnamese), you can upgrade your licence.
We offer the option to upgrade either smaller font packages to larger ones, or upgrade single-user licenses to multiple-user licenses. For example, you can buy a single-user license for Fedra Sans Light for €90 now, and upgrade it later to a complete package for the total price of the package...
The main variables that affect the price of a font are: the number of selected styles, number of users, and selected format. For example, our OpenType Std fonts are €90 per style, while OpenType Pro fonts are €120 per style (for single-user licenses).
Choose a typeface you would like to purchase and click on the blue Buying options button on its page. You will be offered the option to select individual typefaces or complete packages, and in some cases a choice of Pro or Std fonts.