A GPU (graphics processing unit) is a specialized electronic circuit designed to rapidly manipulate and alter memory to accelerate the creation of images in a frame buffer intended for output to a display.
Xeon Phi is a coprocessor computer architecture developed by Intel. Based on Intel Many Integrated Core Architecture (MIC), it complement the industry-leading performance and energy-efficiency of the Intel Xeon processor E5 family to enable dramatic performance gains for some of today’s most demanding applications.
VGA (Video Graphics Array) refers specifically to the display hardware. Higher-resolution and other display modes are achievable, even with standard cards and most standard monitors.