Highwire is the same as tight wire but at much greater height. Although there is no official height when tight wire becomes high wire, generally a wire over twenty feet high will be regarded as a high wire act. Traditionally, the difference is in style of performance.
Skywalk is a form somewhat akin to highwire, but generally defined by its length and height, often taking place outdoors at great heights, often between skyscrapers, gorges, mountains or other natural and man-made landscapes. Source: Wikipedia