[1] In a general sense, Quartz or Quartz technologies can refer to almost every part of the macOS graphics model from the rendering layer down to the compositor including Core Image and Core Video.
Quartz can render text with sub-pixel precision; graphics are limited to more traditional anti-aliasing, which is the default mode of operation but can be turned off.
However, GPU rendering was not enabled by default due to potential video redraw issues or kernel panics.
In Mac OS X Jaguar and later, the Quartz Compositor can use the graphics accelerator (GPU) to vastly improve composition performance.
This technology is known as Quartz Extreme and is enabled automatically on systems with supported graphics cards.