Apple Advanced Typography

Apple Advanced Typography (AAT) is Apple Inc.'s computer technology for advanced font rendering, supporting internationalization and complex features for typographers, a successor to Apple's little-used QuickDraw GX font technology of the mid-1990s. It is a set of extensions to the TrueType outline font standard, with smartfont features similar to the OpenType font format that was developed by Adobe and Microsoft, and to Graphite.

Source: Wikipedia — Apple Advanced Typography (CC BY-SA 4.0)