The Helvetica font is a popular font used by many advertising agencies all over the world. Its use is most widely seen in signage of different types. The Helvetica is essentially a neutral font and is useful when the font has to be such that it does not convey any meaning of its own.
This gives graphic designers a lot of leeway in using this font as they wish in different graphic designs. The Helvetica Black Oblique on the other hand, adds character to the otherwise neutral Helvetica. The black version of this font is darker and bolder than the Helvetica Bold Oblique font.
See also: Free Helvetica Font: Helvetica Oblique