What practice application will this serve in a desktop that a video card cannot do?
With the proper coding, these can be used for processing server loads....running VM's....anything a regular desktop processor can do. These things also don't rely on an API for processing as they are designed to run native x86 instructions. So, anything that relies on x86 instructions....these processors can do. Graphics cards are really quite limited in what they can do compared to the Xeon Phi cards.