Accessibility Toolkit
Appearance
Accessibility Toolkit refers in particular to the GNOME ATK.
The ATK is a developer toolkit which allows programmers to use common GNOME accessibility features in their applications. This includes such features as high-contrast visual themes for the visually-impaired and keyboard behaviour modifiers (e.g. Sticky Keys) for those with diminished motor control.
Links
GNOME Accessibility Project - http://developer.gnome.org/projects/gap/