EPS2XX can convert an existing EPS file to 4 other formats: PDF, JPG, PNG, and TIFF (one at a time or several at once) using Ghostscript. EPS2XX reads an eps file, modifies the bounding box and creates output file(s) file whose size is/are determined by the bounding box from the eps file and not by the paper size. This can not be accomplished by using Ghostscript only.
This tool is especially suited for LaTeX (TeX) users who want to create pdf documents on the fly (by including pdf graphics and using either pdftex or pdflatex). An example would be, if you are using LaTeX (TeX) to typeset documents then the usual (simple) way to include graphics is to include eps graphics using for example (if there exists myfigure.eps)
To use pdflatex (pdftex) you do not need to change anything but provide another file myfigure.pdf in the same directory along with myfigure.eps. And this file, of course, can be generated by EPS2XXX.