Many systems have had that label put on them like the Cray CX1[2] and the Apple Power Mac G4.
[3] Generally, though the label is used on computers that are high end workstations and servers and have multiple processors and is small enough to fit on a desk or to the side.
They can be used in medical applications for processing brain and body scans, resulting in faster diagnosis.
[5] Another application is persistent aerial surveillance where large amounts of video data need to be processed and stored.
One more use is in the field of data analysis which requires large amounts of computational power.